subject:"Re\: Why even physicists still don’t understand quantum theory 100 years on"

Bruce,

I’ve already provided multiple counterexamples, but you keep repeating the
same assertions as if that’s a substitute for addressing them. If you’re so
convinced of your "proof," publish it instead of endlessly posturing here.
Otherwise, this is just noise.

Quentin

Le mer. 26 févr. 2025, 22:08, Bruce Kellett  a
écrit :

> On Wed, Feb 26, 2025 at 10:26 PM Quentin Anciaux 
> wrote:
>
>> You are still assuming that each measurement results in a discrete split
>> with exactly one observer per branch, which is an interpretation, not a
>> derivation. Nothing in the Schrödinger equation forces branches to be
>> discrete rather than continuously superposed structures with relative
>> measure. Your reasoning assumes what it wants to prove: that branching is a
>> countable process rather than a differentiation of an already superposed
>> structure.
>>
>
> I find it interesting that you haven't even attempted to answer the
> detailed argument that I made (below). That, to me, suggests that you do
> not have any coherent response to offer. So you just repeat your normal
> smoke-and-mirrors trick and hope that I will be diverted away from the main
> points. I think you need to up your game if you want to make any progress
> here.
>
> Bruce
>
>
>> Publish it, what are you afraid of? Being proved wrong?
>>
>> Quentin
>>
>> Le mer. 26 févr. 2025, 11:04, Bruce Kellett  a
>> écrit :
>>
>>> On Wed, Feb 26, 2025 at 7:08 PM Quentin Anciaux 
>>> wrote:
>>>

 You’re still misrepresenting the argument. It’s not branch counting
 under another name, it’s about how measure determines observer frequencies.
 The issue is whether the number of observer instances scales with amplitude
 squared, not whether we simply count branches. If all branches were
 weighted equally, MWI would have been dead on arrival, because it wouldn’t
 match experiments.

 The claim that “one observer per branch” is a direct consequence of
 unitary evolution is just an assumption, it’s not something derived from
 the Schrödinger equation.

>>>
>>> It is derived from that, or the Schrodinger equation enhanced with
>>> unitary evolution and the linearity of Hilbert space.
>>>
>>> Since you clearly don't get it. Let me spell it out in baby steps.
>>>
>>> We start from the wave function for some system, say |psi>. This is the
>>> expanded in some basis like |psi> = a|0> + b|1>, where I have taken a two
>>> dimensional space for clarity and convenience, although the argument is
>>> easily expanded to an arbitrary number of independent basis states.
>>>
>>> We then measure this state (or subject it to some interaction).
>>> |psi>|O>|E> where |O> is an observer, and |E> is the environment which can
>>> include anything else that is relevant. Linear unitary evolution then
>>> entangles both the observer and the environment with the object state:
>>>
>>>  |psi>|O>|E> = (a|0> + b|1>)|O>|E> --> a|O sees zero>|E records
>>> zero>|0> + b|O sees one>|E records one>|1>,
>>>
>>> One can readily see that there is one, and only one, copy of the
>>> observer for each branch. Decoherence renders these branches approximately
>>> orthogonal, and leads to the notion of independent worlds. The argument
>>> can, of course, be readily generalized to a state with any number of basis
>>> vectors. In no case, do we get more than one copy of the observer on any
>>> branch, and there are no branches without a copy of the observer.
>>>
>>> All of this is just elementary linear unitary evolution, taught in
>>> general quantum mechanics courses. If you want to deny this, you have to go
>>> to some other theory which is incompatible with quantum mechanics.
>>>
>>> Bruce
>>>
>> --
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

On Wed, Feb 26, 2025 at 10:26 PM Quentin Anciaux  wrote:

> You are still assuming that each measurement results in a discrete split
> with exactly one observer per branch, which is an interpretation, not a
> derivation. Nothing in the Schrödinger equation forces branches to be
> discrete rather than continuously superposed structures with relative
> measure. Your reasoning assumes what it wants to prove: that branching is a
> countable process rather than a differentiation of an already superposed
> structure.
>

I find it interesting that you haven't even attempted to answer the
detailed argument that I made (below). That, to me, suggests that you do
not have any coherent response to offer. So you just repeat your normal
smoke-and-mirrors trick and hope that I will be diverted away from the main
points. I think you need to up your game if you want to make any progress
here.

Bruce


> Publish it, what are you afraid of? Being proved wrong?
>
> Quentin
>
> Le mer. 26 févr. 2025, 11:04, Bruce Kellett  a
> écrit :
>
>> On Wed, Feb 26, 2025 at 7:08 PM Quentin Anciaux 
>> wrote:
>>
>>>
>>> You’re still misrepresenting the argument. It’s not branch counting
>>> under another name, it’s about how measure determines observer frequencies.
>>> The issue is whether the number of observer instances scales with amplitude
>>> squared, not whether we simply count branches. If all branches were
>>> weighted equally, MWI would have been dead on arrival, because it wouldn’t
>>> match experiments.
>>>
>>> The claim that “one observer per branch” is a direct consequence of
>>> unitary evolution is just an assumption, it’s not something derived from
>>> the Schrödinger equation.
>>>
>>
>> It is derived from that, or the Schrodinger equation enhanced with
>> unitary evolution and the linearity of Hilbert space.
>>
>> Since you clearly don't get it. Let me spell it out in baby steps.
>>
>> We start from the wave function for some system, say |psi>. This is the
>> expanded in some basis like |psi> = a|0> + b|1>, where I have taken a two
>> dimensional space for clarity and convenience, although the argument is
>> easily expanded to an arbitrary number of independent basis states.
>>
>> We then measure this state (or subject it to some interaction).
>> |psi>|O>|E> where |O> is an observer, and |E> is the environment which can
>> include anything else that is relevant. Linear unitary evolution then
>> entangles both the observer and the environment with the object state:
>>
>>  |psi>|O>|E> = (a|0> + b|1>)|O>|E> --> a|O sees zero>|E records
>> zero>|0> + b|O sees one>|E records one>|1>,
>>
>> One can readily see that there is one, and only one, copy of the observer
>> for each branch. Decoherence renders these branches approximately
>> orthogonal, and leads to the notion of independent worlds. The argument
>> can, of course, be readily generalized to a state with any number of basis
>> vectors. In no case, do we get more than one copy of the observer on any
>> branch, and there are no branches without a copy of the observer.
>>
>> All of this is just elementary linear unitary evolution, taught in
>> general quantum mechanics courses. If you want to deny this, you have to go
>> to some other theory which is incompatible with quantum mechanics.
>>
>> Bruce
>>
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-26 Thread Alan Grayson



On Wednesday, February 26, 2025 at 5:38:02 AM UTC-7 John Clark wrote:

On Wed, Feb 26, 2025 at 12:41 AM Brent Meeker  wrote:



* > Have you read Scott Aaronson's blog on MWI. 
https://scottaaronson.blog/?p=1103 *


*> "MWI really is just the “obvious, straightforward” reading of quantum 
mechanics itself, if you take quantum mechanics literally as a description 
of the whole universe, and assume nothing new will ever be discovered that 
changes the picture."*


*I agree with Aaronson that it's going too far to try to make an analogy 
between MMI and the Copernican revolution because it's hard to imagine any 
new discovery which would make us reconsider our conclusion that the Earth 
is not the center of the universe, however it it is possible to imagine 
something that would cause us to conclude that many worlds is wrong, 
objective collapse is one example.  *

> *"**as soon as we postulate any decoherence (whatever its source) that 
occurs below the level of everyday experience, and that’s truly 
irreversible for fundamental physical reasons … at that point, I would say 
that we can now fully explain our experience without any reference to 
parallel copies of ourselves in other branches, and are therefore not 
forced into MWIism."*


*Apparently Aaronson agrees with me that Many Worlds is a legitimate 
scientific theory because it is falsifiable.  *


*Since the worlds are disjoint, they don't interact, and the MWI is 
obviously NOT falsifiable. AG *


 *> "**And MWIism isn’t something that has great appeal to me unless I’m 
forced into it. But I suspect Deutsch would disagree here."*


*On this issue I admit to being emotionally closer to Deutsch than 
Aaronson, but that is irrelevant. I liked Fred Hoyle and steady state 
cosmology had great emotional appeal to me, but that didn't prevent it from 
being dead wrong. **I have my likes and dislikes, and the universe has 
its. *

*John K ClarkSee what's on my new list at  Extropolis 
*

hfg

 

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-26 Thread John Clark

On Wed, Feb 26, 2025 at 12:41 AM Brent Meeker  wrote:

>
> * > Have you read Scott Aaronson's blog on MWI.
> https://scottaaronson.blog/?p=1103 *
>

*> "MWI really is just the “obvious, straightforward” reading of quantum
> mechanics itself, if you take quantum mechanics literally as a description
> of the whole universe, and assume nothing new will ever be discovered that
> changes the picture."*

*I agree with Aaronson that it's going too far to try to make an analogy
between MMI and the Copernican revolution because it's hard to imagine any
new discovery which would make us reconsider our conclusion that the Earth
is not the center of the universe, however it it is possible to imagine
something that would cause us to conclude that many worlds is wrong,
objective collapse is one example.  *

> *"**as soon as we postulate any decoherence (whatever its source) that
> occurs below the level of everyday experience, and that’s truly
> irreversible for fundamental physical reasons … at that point, I would say
> that we can now fully explain our experience without any reference to
> parallel copies of ourselves in other branches, and are therefore not
> forced into MWIism."*

*Apparently Aaronson agrees with me that Many Worlds is a legitimate
scientific theory because it is falsifiable.  *

 *> "**And MWIism isn’t something that has great appeal to me unless I’m
> forced into it. But I suspect Deutsch would disagree here."*

*On this issue I admit to being emotionally closer to Deutsch than
Aaronson, but that is irrelevant. I liked Fred Hoyle and steady state
cosmology had great emotional appeal to me, but that didn't prevent it from
being dead wrong. **I have my likes and dislikes, and the universe has
its. *

*John K ClarkSee what's on my new list at  Extropolis
*

hfg

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Re: Why even physicists still don’t understand quantum theory 100 years on

Publishing isn’t about ‘being right,’ it’s about subjecting claims to
proper scrutiny. If your argument truly refutes MWI, it would be one of the
most significant results in quantum foundations—yet you choose to keep it
confined to email threads. That speaks volumes.

Quentin

Le mer. 26 févr. 2025, 11:09, Bruce Kellett  a
écrit :

> On Wed, Feb 26, 2025 at 9:54 PM Quentin Anciaux 
> wrote:
>
>> I am discussing Everettian theory, just not your rigid and reductionist
>> version of it.
>>
>
> No, you are not. The theory you are using to argue against my position is
> just some arbitrary concoction of your own. I hope that my more detailed
> account of how linear unitary evolution leads to just one, and only one,
> observer per Everettian branch convinces you that you are not using
> standard Everettian theory.
>
> If you believe differentiation of pre-existing superposed branches is
>> 'madcap,' then you haven't truly engaged with the problem. Again, if your
>> argument is as conclusive as you claim, publish it and let it stand to
>> scrutiny.
>>
>
> I don't have to publish to be right.
>
> Bruce
>
> --
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

You are still assuming that each measurement results in a discrete split
with exactly one observer per branch, which is an interpretation, not a
derivation. Nothing in the Schrödinger equation forces branches to be
discrete rather than continuously superposed structures with relative
measure. Your reasoning assumes what it wants to prove: that branching is a
countable process rather than a differentiation of an already superposed
structure.

Publish it, what are you afraid of? Being proved wrong?

Quentin

Le mer. 26 févr. 2025, 11:04, Bruce Kellett  a
écrit :

> On Wed, Feb 26, 2025 at 7:08 PM Quentin Anciaux 
> wrote:
>
>> Le mer. 26 févr. 2025, 01:53, Brent Meeker  a
>> écrit :
>>
>>> On 2/25/2025 5:09 PM, Russell Standish wrote:
>>>
>>> On Wed, Feb 26, 2025 at 11:01:11AM +1100, Bruce Kellett wrote:
>>>
>>> On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
>>>
>>> Your claim that "one observer per branch" follows directly from 
>>> unitary
>>> evolution is an assumption, not a derivation.
>>>
>>>
>>> No, it is a straightforward derivation from the formalism. If you don't
>>> understand that, it is just further confirmation of the fact that you
>>> understand very little about quantum mechanics.
>>>
>>> Not at all - it is an assumption you're making, and the nub of the entire
>>> argument between you and Quentin.
>>>
>>> Do you understand Quentin's theory?  ISTM it's just "Observer counting"
>>> where the counts instantiate the Born rule ex hypothesi.  It's branch
>>> counting by another name.
>>>
>>> Brent
>>>
>>
>> Brent,
>>
>> You’re still misrepresenting the argument. It’s not branch counting under
>> another name, it’s about how measure determines observer frequencies. The
>> issue is whether the number of observer instances scales with amplitude
>> squared, not whether we simply count branches. If all branches were
>> weighted equally, MWI would have been dead on arrival, because it wouldn’t
>> match experiments.
>>
>> The claim that “one observer per branch” is a direct consequence of
>> unitary evolution is just an assumption, it’s not something derived from
>> the Schrödinger equation.
>>
>
> It is derived from that, or the Schrodinger equation enhanced with unitary
> evolution and the linearity of Hilbert space.
>
> Since you clearly don't get it. Let me spell it out in baby steps.
>
> We start from the wave function for some system, say |psi>. This is the
> expanded in some basis like |psi> = a|0> + b|1>, where I have taken a two
> dimensional space for clarity and convenience, although the argument is
> easily expanded to an arbitrary number of independent basis states.
>
> We then measure this state (or subject it to some interaction).
> |psi>|O>|E> where |O> is an observer, and |E> is the environment which can
> include anything else that is relevant. Linear unitary evolution then
> entangles both the observer and the environment with the object state:
>
>  |psi>|O>|E> = (a|0> + b|1>)|O>|E> --> a|O sees zero>|E records
> zero>|0> + b|O sees one>|E records one>|1>,
>
> One can readily see that there is one, and only one, copy of the observer
> for each branch. Decoherence renders these branches approximately
> orthogonal, and leads to the notion of independent worlds. The argument
> can, of course, be readily generalized to a state with any number of basis
> vectors. In no case, do we get more than one copy of the observer on any
> branch, and there are no branches without a copy of the observer.
>
> All of this is just elementary linear unitary evolution, taught in general
> quantum mechanics courses. If you want to deny this, you have to go to some
> other theory which is incompatible with quantum mechanics.
>
> Bruce
>
> --
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

On Wed, Feb 26, 2025 at 9:54 PM Quentin Anciaux  wrote:

> I am discussing Everettian theory, just not your rigid and reductionist
> version of it.
>

No, you are not. The theory you are using to argue against my position is
just some arbitrary concoction of your own. I hope that my more detailed
account of how linear unitary evolution leads to just one, and only one,
observer per Everettian branch convinces you that you are not using
standard Everettian theory.

If you believe differentiation of pre-existing superposed branches is
> 'madcap,' then you haven't truly engaged with the problem. Again, if your
> argument is as conclusive as you claim, publish it and let it stand to
> scrutiny.
>

I don't have to publish to be right.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

On Wed, Feb 26, 2025 at 7:08 PM Quentin Anciaux  wrote:

> Le mer. 26 févr. 2025, 01:53, Brent Meeker  a
> écrit :
>
>> On 2/25/2025 5:09 PM, Russell Standish wrote:
>>
>> On Wed, Feb 26, 2025 at 11:01:11AM +1100, Bruce Kellett wrote:
>>
>> On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
>>
>> Your claim that "one observer per branch" follows directly from 
>> unitary
>> evolution is an assumption, not a derivation.
>>
>>
>> No, it is a straightforward derivation from the formalism. If you don't
>> understand that, it is just further confirmation of the fact that you
>> understand very little about quantum mechanics.
>>
>> Not at all - it is an assumption you're making, and the nub of the entire
>> argument between you and Quentin.
>>
>> Do you understand Quentin's theory?  ISTM it's just "Observer counting"
>> where the counts instantiate the Born rule ex hypothesi.  It's branch
>> counting by another name.
>>
>> Brent
>>
>
> Brent,
>
> You’re still misrepresenting the argument. It’s not branch counting under
> another name, it’s about how measure determines observer frequencies. The
> issue is whether the number of observer instances scales with amplitude
> squared, not whether we simply count branches. If all branches were
> weighted equally, MWI would have been dead on arrival, because it wouldn’t
> match experiments.
>
> The claim that “one observer per branch” is a direct consequence of
> unitary evolution is just an assumption, it’s not something derived from
> the Schrödinger equation.
>

It is derived from that, or the Schrodinger equation enhanced with unitary
evolution and the linearity of Hilbert space.

Since you clearly don't get it. Let me spell it out in baby steps.

We start from the wave function for some system, say |psi>. This is the
expanded in some basis like |psi> = a|0> + b|1>, where I have taken a two
dimensional space for clarity and convenience, although the argument is
easily expanded to an arbitrary number of independent basis states.

We then measure this state (or subject it to some interaction). |psi>|O>|E>
where |O> is an observer, and |E> is the environment which can include
anything else that is relevant. Linear unitary evolution then entangles
both the observer and the environment with the object state:

 |psi>|O>|E> = (a|0> + b|1>)|O>|E> --> a|O sees zero>|E records
zero>|0> + b|O sees one>|E records one>|1>,

One can readily see that there is one, and only one, copy of the observer
for each branch. Decoherence renders these branches approximately
orthogonal, and leads to the notion of independent worlds. The argument
can, of course, be readily generalized to a state with any number of basis
vectors. In no case, do we get more than one copy of the observer on any
branch, and there are no branches without a copy of the observer.

All of this is just elementary linear unitary evolution, taught in general
quantum mechanics courses. If you want to deny this, you have to go to some
other theory which is incompatible with quantum mechanics.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

I am discussing Everettian theory, just not your rigid and reductionist
version of it. If you believe differentiation of pre-existing superposed
branches is 'madcap,' then you haven't truly engaged with the problem.
Again, if your argument is as conclusive as you claim, publish it and let
it stand to scrutiny.

Quentin

Le mer. 26 févr. 2025, 10:38, Bruce Kellett  a
écrit :

> On Wed, Feb 26, 2025 at 7:02 PM Quentin Anciaux 
> wrote:
>
>> Bruce,
>>
>> You claim that your argument proves MWI is inconsistent with the Born
>> rule, but what you’ve actually shown is that naive branch counting doesn’t
>> work, something Everettians already acknowledge. The real question is
>> whether measure, derived from amplitudes, determines observer frequencies,
>> and your argument does not disprove that.
>>
>> Decoherence is not about making branches "disappear", it’s about
>> preventing interference, which allows classical-like behavior to emerge. If
>> low-amplitude branches exist but do not significantly contribute to
>> observer experiences, that’s exactly what would give rise to Born-rule
>> statistics. Your response doesn’t refute this; it simply denies that
>> amplitudes matter beyond formal calculations, which contradicts all of
>> quantum theory outside of measurement.
>>
>> You state that unitary evolution directly leads to "one observer per
>> branch," but that’s an assumption based on a discrete branching picture
>> that Everett himself didn’t use. The wavefunction remains continuous, and
>> what we call "a branch" is just an approximation of decoherence-selected
>> states.
>>
>> If you believe the Born rule must simply be assumed rather than derived,
>> then fine, but that applies to all interpretations, not just MWI. If you
>> claim MWI is falsified, then demonstrate why no derivation of the Born rule
>> from unitary evolution is possible, instead of repeating that it hasn’t
>> been done. And if your so-called "proof" is airtight, publish it, surely
>> the physics community will be thrilled to see a definitive refutation of
>> MWI. But you won’t, because you know it’s flawed.
>>
>> Instead, you’d rather sit here, dismissing any disagreement as stupidity
>> while avoiding any real engagement with the open question. You’re not
>> debating in good faith, you’re just clinging to your priors and throwing
>> insults at those who don’t share them.
>>
>> If you’re so convinced of your argument, be decent enough to confront it
>> with actual peer review instead of just parading it around this list. Or is
>> that too much to ask?
>>
>
>
> You are repeating yourself. And your arguments are all based on your own
> madcap theory. Why don't you actually approach the questions from the point
> of view of standard Everettian theory?
>
> Bruce
>
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

On Wed, Feb 26, 2025 at 7:02 PM Quentin Anciaux  wrote:

> Bruce,
>
> You claim that your argument proves MWI is inconsistent with the Born
> rule, but what you’ve actually shown is that naive branch counting doesn’t
> work, something Everettians already acknowledge. The real question is
> whether measure, derived from amplitudes, determines observer frequencies,
> and your argument does not disprove that.
>
> Decoherence is not about making branches "disappear", it’s about
> preventing interference, which allows classical-like behavior to emerge. If
> low-amplitude branches exist but do not significantly contribute to
> observer experiences, that’s exactly what would give rise to Born-rule
> statistics. Your response doesn’t refute this; it simply denies that
> amplitudes matter beyond formal calculations, which contradicts all of
> quantum theory outside of measurement.
>
> You state that unitary evolution directly leads to "one observer per
> branch," but that’s an assumption based on a discrete branching picture
> that Everett himself didn’t use. The wavefunction remains continuous, and
> what we call "a branch" is just an approximation of decoherence-selected
> states.
>
> If you believe the Born rule must simply be assumed rather than derived,
> then fine, but that applies to all interpretations, not just MWI. If you
> claim MWI is falsified, then demonstrate why no derivation of the Born rule
> from unitary evolution is possible, instead of repeating that it hasn’t
> been done. And if your so-called "proof" is airtight, publish it, surely
> the physics community will be thrilled to see a definitive refutation of
> MWI. But you won’t, because you know it’s flawed.
>
> Instead, you’d rather sit here, dismissing any disagreement as stupidity
> while avoiding any real engagement with the open question. You’re not
> debating in good faith, you’re just clinging to your priors and throwing
> insults at those who don’t share them.
>
> If you’re so convinced of your argument, be decent enough to confront it
> with actual peer review instead of just parading it around this list. Or is
> that too much to ask?
>


You are repeating yourself. And your arguments are all based on your own
madcap theory. Why don't you actually approach the questions from the point
of view of standard Everettian theory?

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

Le mer. 26 févr. 2025, 01:53, Brent Meeker  a écrit :

>
>
> On 2/25/2025 5:09 PM, Russell Standish wrote:
>
> On Wed, Feb 26, 2025 at 11:01:11AM +1100, Bruce Kellett wrote:
>
> On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
>
> Your claim that "one observer per branch" follows directly from 
> unitary
> evolution is an assumption, not a derivation.
>
>
> No, it is a straightforward derivation from the formalism. If you don't
> understand that, it is just further confirmation of the fact that you
> understand very little about quantum mechanics.
>
> Not at all - it is an assumption you're making, and the nub of the entire
> argument between you and Quentin.
>
> Do you understand Quentin's theory?  ISTM it's just "Observer counting"
> where the counts instantiate the Born rule ex hypothesi.  It's branch
> counting by another name.
>
> Brent
>

Brent,

You’re still misrepresenting the argument. It’s not branch counting under
another name, it’s about how measure determines observer frequencies. The
issue is whether the number of observer instances scales with amplitude
squared, not whether we simply count branches. If all branches were
weighted equally, MWI would have been dead on arrival, because it wouldn’t
match experiments.

The claim that “one observer per branch” is a direct consequence of unitary
evolution is just an assumption, it’s not something derived from the
Schrödinger equation. Everett’s original formulation was about relative
states, not discrete worlds with single, isolated observers. If you start
from a continuously evolving wavefunction, then what we call “a branch” is
a convenient approximation, not a fundamental unit.

If you’re convinced that observer frequencies cannot be tied to amplitudes,
the burden is on you to explain why amplitudes govern every other quantum
phenomenon yet suddenly become irrelevant when it comes to probability. You
need more than “MWI doesn’t work”, you need to show why no measure-based
derivation of the Born rule is possible, rather than dismissing attempts to
derive it. Also implying 1 observer per branch implies some kind of
duplication at every measurements whereas my view implies differentiation
of pre-existing infinitely superposed branches.

Quentin

>
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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

You claim that your argument proves MWI is inconsistent with the Born rule,
but what you’ve actually shown is that naive branch counting doesn’t work,
something Everettians already acknowledge. The real question is whether
measure, derived from amplitudes, determines observer frequencies, and your
argument does not disprove that.

Decoherence is not about making branches "disappear", it’s about preventing
interference, which allows classical-like behavior to emerge. If
low-amplitude branches exist but do not significantly contribute to
observer experiences, that’s exactly what would give rise to Born-rule
statistics. Your response doesn’t refute this; it simply denies that
amplitudes matter beyond formal calculations, which contradicts all of
quantum theory outside of measurement.

You state that unitary evolution directly leads to "one observer per
branch," but that’s an assumption based on a discrete branching picture
that Everett himself didn’t use. The wavefunction remains continuous, and
what we call "a branch" is just an approximation of decoherence-selected
states.

If you believe the Born rule must simply be assumed rather than derived,
then fine, but that applies to all interpretations, not just MWI. If you
claim MWI is falsified, then demonstrate why no derivation of the Born rule
from unitary evolution is possible, instead of repeating that it hasn’t
been done. And if your so-called "proof" is airtight, publish it, surely
the physics community will be thrilled to see a definitive refutation of
MWI. But you won’t, because you know it’s flawed.

Instead, you’d rather sit here, dismissing any disagreement as stupidity
while avoiding any real engagement with the open question. You’re not
debating in good faith, you’re just clinging to your priors and throwing
insults at those who don’t share them.

If you’re so convinced of your argument, be decent enough to confront it
with actual peer review instead of just parading it around this list. Or is
that too much to ask?

Quentin

Le mer. 26 févr. 2025, 00:01, Bruce Kellett  a
écrit :

>
> On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
>>
>> Bruce,
>>
>> Your response assumes that unitary evolution inherently produces "one
>> observer per branch" in a discrete way, but that’s not what follows from
>> the wavefunction’s continuous structure. Everett’s relative state
>> formulation does not propose discrete worlds but rather an evolving
>> superposition where decoherence prevents interference. The fact that we
>> describe macroscopic branches as "splitting" is a convenient approximation,
>> not a fundamental aspect of the theory.
>>
>>
> Everett did not know about decoherence. That idea emerged only about30
> years after Evefrett's work.
>
> The key point you keep ignoring is that amplitudes are not just "carried
>> along" without meaning—they define the structure of the wavefunction, and
>> decoherence prevents low-amplitude branches from significantly contributing
>> to observer experiences.
>>
>>
> That is simply nonsense. Decoherence does no such thing. You just keep on
> making things up, and you are not arguing for Everettian QM at all. You are
> obsessed by your own half-baked ideas about computationalism.
>
>
>> Your claim that "one observer per branch" follows directly from unitary
>> evolution is an assumption, not a derivation.
>>
>>
> No, it is a straightforward derivation from the formalism. If you don't
> understand that, it is just further confirmation of the fact that you
> understand very little about quantum mechanics.
>
>
> If you insist that unitary evolution cannot produce probability weights,
>> then your argument applies equally to any interpretation of quantum
>> mechanics. The Born rule is a fact of experiment, and any valid
>> interpretation must explain it.
>>
>>
> Why? It can just be assumed as a way to relate the theory to experimental
> results.
>
> If you believe MWI cannot do so, you must show why—not just assert that it
>> "hasn’t been done" while dismissing attempts to derive it. Assume your
>> pride, publish and get the glory.
>>
>>
> I have shown that MWI is not consistent with the Born rule. If you have
> not understood the proof, then that is your lack of insight, not a failure
> of the proof.
> The trouble with your attempts to undermine my arguments is that you
> resort to many unfounded assertions based on your half-baked
> computationalist ideas. You do not argue from the basis of unitary quantum
> mechanics, so your arguments are valueless.
>
> Bruce
>
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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread Brent Meeker

Have you read Scott Aaronson's blog on MWI.

https://scottaaronson.blog/?p=1103

I especially recommend his answer to Greg Egan's comment.

Brent

On 2/25/2025 6:56 PM, Liz R wrote:

On Thursday, 6 February 2025 at 07:42:57 UTC+13 Alan Grayson wrote:

And why the MWI is unverifiable and tantamount to a fantasy. AG

I don't know if David Deutsch still considers this a valid response,
but it's come a darn sight closer to reality since he suggested it
back in the 90s (I think). He claimed that explaining a sufficiently
advanced quantum computer requires the MWI. The other day I saw a
headline about the latest quantum computer that could - in principle,
of course - outperform a classical computer by a factor of many
trillions. Unfortunately I can't remember where I saw it, but there
was some huge age-of-the-universe-plus claim involved.

So, if we assume that a quantum computer can reach the point where it
outperforms a classical computer by more than the theoretical limit -
something involving the Bekenstein Bound and Margolus-Levitin Limit,
apparently, which ChatGPT reliably informs me for a volume V and time
t comes down to

Max computations∼(c^5/ ℏG). tV

(c, G and h bar having their usual values).

So if this is possible, the MWI would become verifiable, in that - to
quote Professor Deutsch - where else can the computations be
performed, except in branches of a multiverse?

Anyway, I don't suppose this will actually be demonstrated anytime
soon, but it is one theoretical test of the MWI, hence it's - very
much in principle - verifiable.

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread Liz R

On Thursday, 6 February 2025 at 07:42:57 UTC+13 Alan Grayson wrote:

And why the MWI is unverifiable and tantamount to a fantasy. AG

I don't know if David Deutsch still considers this a valid response, but
it's come a darn sight closer to reality since he suggested it back in the
90s (I think). He claimed that explaining a sufficiently advanced quantum
computer requires the MWI. The other day I saw a headline about the latest
quantum computer that could - in principle, of course - outperform a
classical computer by a factor of many trillions. Unfortunately I can't
remember where I saw it, but there was some huge age-of-the-universe-plus
claim involved.

So, if we assume that a quantum computer can reach the point where it
outperforms a classical computer by more than the theoretical limit -
something involving the Bekenstein Bound and Margolus-Levitin Limit,
apparently, which ChatGPT reliably informs me for a volume V and time t
comes down to

Max computations∼(c^5/ ℏG) . tV

(c, G and h bar having their usual values).

So if this is possible, the MWI would become verifiable, in that - to quote
Professor Deutsch - where else can the computations be performed, except in
branches of a multiverse?

Anyway, I don't suppose this will actually be demonstrated anytime soon,
but it is one theoretical test of the MWI, hence it's - very much in
principle - verifiable.

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread Brent Meeker




On 2/25/2025 5:09 PM, Russell Standish wrote:

On Wed, Feb 26, 2025 at 11:01:11AM +1100, Bruce Kellett wrote:

 On 2/24/2025 6:09 PM, Quentin Anciaux wrote:

 Your claim that "one observer per branch" follows directly from unitary
 evolution is an assumption, not a derivation.


No, it is a straightforward derivation from the formalism. If you don't
understand that, it is just further confirmation of the fact that you
understand very little about quantum mechanics.

Not at all - it is an assumption you're making, and the nub of the entire
argument between you and Quentin.
Do you understand Quentin's theory?  ISTM it's just "Observer counting" 
where the counts instantiate the Born rule ex hypothesi. It's branch 
counting by another name.


Brent






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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread Bruce Kellett

On Wed, Feb 26, 2025 at 12:09 PM Russell Standish 
wrote:

> On Wed, Feb 26, 2025 at 11:01:11AM +1100, Bruce Kellett wrote:
> >
> > On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
> >
> > Your claim that "one observer per branch" follows directly from
> unitary
> > evolution is an assumption, not a derivation.
> >
> >
> > No, it is a straightforward derivation from the formalism. If you don't
> > understand that, it is just further confirmation of the fact that you
> > understand very little about quantum mechanics.
>
> Not at all - it is an assumption you're making, and the nub of the entire
> argument between you and Quentin.
>

If you don't see it as a derivation from unitary QM and Everett's ideas
then you are missing something important about quantum mechanics.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread Russell Standish

On Wed, Feb 26, 2025 at 11:01:11AM +1100, Bruce Kellett wrote:
> 
> On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
> 
> Your claim that "one observer per branch" follows directly from 
> unitary
> evolution is an assumption, not a derivation.
> 
> 
> No, it is a straightforward derivation from the formalism. If you don't
> understand that, it is just further confirmation of the fact that you
> understand very little about quantum mechanics.

Not at all - it is an assumption you're making, and the nub of the entire
argument between you and Quentin.


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Principal, High Performance Coders hpco...@hpcoders.com.au
  http://www.hpcoders.com.au


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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread Brent Meeker




On 2/25/2025 5:17 AM, John Clark wrote:
The symmetry of envariance ensures that, within your branch, _the 
environment has conspired to align with one definite outcome_ (say, 
heads), hiding the other possibilities (tails) in a way that’s 
consistent with the branching process.
I reads just as well "in a way that's consistent with the survival of 
only one branch per the Born rule."


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-25 Thread John Clark

On Mon, Feb 24, 2025 at 6:07 PM Brent Meeker  wrote:

> *>> Zurek’s "envariance" means that if a system is  entangled with its
>> environment then  mathematics insists we assign equal probabilities to
>> outcomes in which the amplitudes in the quantum state’s expansion are
>> equal, and obviously the squared magnitudes of the amplitudes. And I don't
>> need to tell you what that leads to.*
>
>
> *> That's not "envariance".  Envariance is Zurek's proposal for how the
> preferred basis problem should be solved.  I guess I did need to tell you
> that.*
>

*I**asked Grok3 (which might be the smartest AI currently available to the
general public) about that and he she or it seems to agree with me.
Envariance doesn't demand that many worlds be true but it is certainly
consistent with it, and there are strong similarities between the two
ideas. You were correct when you said because of envariance "interaction
with the environment must select only certain bases which survive
decoherence" but those "certain bases" that survive are all pointer states,
quantum states that remains stable under environmental interactions,
particularly during measurement processes; it's why the POINTER on the dial
of a GR device always POINTS to spin up or spin down and nothing in
between, and why you always see either a live cat or a dead cat and nothing
in between. Pointer States are unusually robust quantum states,
mathematically they are the interaction Hamiltonian between the system and
its environment, and "you" is part of the environment.*

*Here is my conversation with Grok3:*

*Me: In quantum mechanics what does the word "envariance" mean?*

*Grok3: "In quantum mechanics, "envariance" is short for
"environment-induced variance," a concept introduced by physicist Wojciech
Zurek as part of his work on quantum decoherence and the emergence of
classical behavior from quantum systems. It describes a special kind of
symmetry in how a quantum system becomes entangled with its environment,
leading to the loss of certain quantum properties—like superposition—and
the appearance of classical-like states."*

*Me: How is that related to the Many Worlds idea?*

*Grok3: "Envariance and the Many Worlds Interpretation (MWI) of quantum
mechanics are connected in that they both deal with how quantum systems
evolve and how we perceive outcomes, but they approach the story from
different angles. Let’s break it down and tie them together intuitively."*

*"In the Many Worlds idea, proposed by Hugh Everett, every quantum
event—like a coin flip or a particle’s spin being measured—doesn’t just
pick one outcome and discard the others. Instead, the universe splits into
multiple branches, one for each possible result. So, if you measure a
spinning coin, one "world" has you seeing heads, and another has you seeing
tails. These worlds don’t talk to each other; they’re separate, parallel
realities, and you’re only aware of the one you’re in. The superposition
doesn’t collapse—it just fans out across these branches."*

*"Envariance, on the other hand, doesn’t explicitly require splitting
universes. It’s about how entanglement with the environment (like when you
flip a coin) creates a symmetry that makes quantum superpositions
unobservable to us. The coin’s heads-and-tails superposition gets tangled
with the environment, and because of envariance, the information about the
superposition is spread out in a way that locks us into seeing just one
outcome locally—like heads—while the full quantum state still exists
globally."*

*"Here’s where they relate: in Many Worlds, the entanglement between the
coin and the environment (and you, the observer) is what drives the
branching. When the coin entangles with the table, and then you look at it,
the quantum state of the whole system—coin + table + you—splits into
branches: one where "you" see heads, and another where "you" see tails.
Envariance fits into this picture as a mechanism explaining why each branch
looks classical to the "you" inside it. The symmetry of envariance ensures
that, within your branch, the environment has conspired to align with one
definite outcome (say, heads), hiding the other possibilities (tails) in a
way that’s consistent with the branching process. The tails outcome isn’t
gone—it’s just in another world, perfectly mirrored by its own
environment."*

*"Intuitively, think of envariance as the backstage crew in a Many Worlds
theater. While Many Worlds says the play splits into multiple performances
(one for each ending), envariance is what makes each performance feel
complete and consistent to its audience—ensuring that the props
(environment) match the script (outcome) in every branch. Without
envariance, the branching might feel more like a chaotic mess than distinct
worlds. So, envariance doesn’t invent Many Worlds, but it helps make the
worlds feel "real" and separate by describing how entanglement locks in the
classical appearances we experience in each one."*

*"They’re not identical—env

Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

That’s exactly the key issue—standard QM introduces a non-unitary
projection, while MWI seeks to replace it with purely unitary evolution.
The challenge is whether probability and the Born rule can emerge naturally
from that evolution rather than being postulated.

Self-locating uncertainty is an attempt to bridge that gap, but as you
point out, it risks assuming the very thing it tries to explain. That’s why
I lean toward computational approaches to consciousness and measure, where
probability could emerge from constraints on information processing rather
than from an explicit collapse rule.

If the projection postulate is just a practical tool and not a fundamental
physical process, then something else must explain why we observe the Born
rule. Whether that’s self-locating uncertainty, decision theory, or
something entirely different remains an open question—but dismissing all
attempts without a working alternative doesn’t resolve the problem either.

Quentin



Le mar. 25 févr. 2025, 07:31, Brent Meeker  a écrit :

>
>
> On 2/24/2025 6:09 PM, Quentin Anciaux wrote:
>
> Bruce,
>
> Your response assumes that unitary evolution inherently produces "one
> observer per branch" in a discrete way, but that’s not what follows from
> the wavefunction’s continuous structure. Everett’s relative state
> formulation does not propose discrete worlds but rather an evolving
> superposition where decoherence prevents interference. The fact that we
> describe macroscopic branches as "splitting" is a convenient approximation,
> not a fundamental aspect of the theory.
>
> The key point you keep ignoring is that amplitudes are not just "carried
> along" without meaning—they define the structure of the wavefunction, and
> decoherence prevents low-amplitude branches from significantly contributing
> to observer experiences. Your claim that "one observer per branch" follows
> directly from unitary evolution is an assumption, not a derivation.
>
> If you insist that unitary evolution cannot produce probability weights,
> then your argument applies equally to any interpretation of quantum
> mechanics. The Born rule is a fact of experiment, and any valid
> interpretation must explain it. If you believe MWI cannot do so, you must
> show why—not just assert that it "hasn’t been done" while dismissing
> attempts to derive it. Assume your pride, publish and get the glory.
>
>  A measurement in QM conforms to the Born rule, but it's not unitary, it's
> a projection operator.  That's how it produces probabilities, it projects
> the unitarily evolved state vector onto the basis eigenvectors of the
> operator.  That's pretty much the problem MWI wants to solve: "How can we
> replace that projection operation with some unitary evolution."  And it
> comes up with "self-locating uncertainty" which postulates the Born rule
> for "selfs".
>
> Brent
>
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>

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Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/24/2025 6:09 PM, Quentin Anciaux wrote:

Bruce,

Your response assumes that unitary evolution inherently produces "one
observer per branch" in a discrete way, but that’s not what follows
from the wavefunction’s continuous structure. Everett’s relative state
formulation does not propose discrete worlds but rather an evolving
superposition where decoherence prevents interference. The fact that
we describe macroscopic branches as "splitting" is a convenient
approximation, not a fundamental aspect of the theory.

The key point you keep ignoring is that amplitudes are not just
"carried along" without meaning—they define the structure of the
wavefunction, and decoherence prevents low-amplitude branches from
significantly contributing to observer experiences. Your claim that
"one observer per branch" follows directly from unitary evolution is
an assumption, not a derivation.

If you insist that unitary evolution cannot produce probability
weights, then your argument applies equally to any interpretation of
quantum mechanics. The Born rule is a fact of experiment, and any
valid interpretation must explain it. If you believe MWI cannot do so,
you must show why—not just assert that it "hasn’t been done" while
dismissing attempts to derive it. Assume your pride, publish and get
the glory.
A measurement in QM conforms to the Born rule, but it's not unitary,
it's a projection operator. That's how it produces probabilities, it
projects the unitarily evolved state vector onto the basis eigenvectors
of the operator. That's pretty much the problem MWI wants to solve:
"How can we replace that projection operation with some unitary
evolution." And it comes up with "self-locating uncertainty" which
postulates the Born rule for "selfs".

Brent

Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

I never claimed that what I’m exploring is standard quantum mechanics—it’s
an attempt to understand where probability and measure come from within
unitary evolution. The Born rule is an empirical fact, and any
interpretation must account for it. If standard QM simply assumes it,
that’s fine for practical purposes, but it leaves an open foundational
question.

The point is not to redefine QM but to explore whether the structure of the
wavefunction itself can justify the probabilities we observe. If you
believe that amplitudes play no role beyond being passive parameters,
that’s an assumption, not a derivation. If the answer is simply "we
postulate the Born rule," then fair enough—but that’s no different from
assuming a single world with one outcome per measurement.

The difference is that I prefer interpretations that try to explain rather
than just assert.

Quentin



Le mar. 25 févr. 2025, 05:56, Bruce Kellett  a
écrit :

> On Tue, Feb 25, 2025 at 3:08 PM Quentin Anciaux 
> wrote:
>
>>
>> Bruce,
>>
>> If we consider that there is always an infinite superposition of
>> branches, then each partition also contains an infinite number of branches,
>> but with different relative measures. The key point is that branches are
>> not discrete objects—they are coarse-grained regions of the wavefunction
>> shaped by decoherence.
>>
>> Unitary evolution does not create additional observers explicitly, but if
>> measure reflects the density of observer instances within the wavefunction,
>> then the number of observers experiencing a particular sequence is not
>> uniform across all branches. This avoids naive branch counting and aligns
>> with how probabilities emerge from continuous distributions rather than
>> discrete events.
>>
>> The challenge is formalizing this within unitary QM, possibly through
>> information-theoretic approaches, measure theory, or even constraints from
>> computational complexity. If amplitudes guide the structure of the
>> wavefunction, why wouldn’t they also influence the distribution of observer
>> instances?
>>
>
> It is good to see that you finally acknowledge that your theory is not
> quantum mechanics.
>
> Bruce
>
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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-24 Thread Bruce Kellett

On Tue, Feb 25, 2025 at 3:08 PM Quentin Anciaux  wrote:

>
> Bruce,
>
> If we consider that there is always an infinite superposition of branches,
> then each partition also contains an infinite number of branches, but with
> different relative measures. The key point is that branches are not
> discrete objects—they are coarse-grained regions of the wavefunction shaped
> by decoherence.
>
> Unitary evolution does not create additional observers explicitly, but if
> measure reflects the density of observer instances within the wavefunction,
> then the number of observers experiencing a particular sequence is not
> uniform across all branches. This avoids naive branch counting and aligns
> with how probabilities emerge from continuous distributions rather than
> discrete events.
>
> The challenge is formalizing this within unitary QM, possibly through
> information-theoretic approaches, measure theory, or even constraints from
> computational complexity. If amplitudes guide the structure of the
> wavefunction, why wouldn’t they also influence the distribution of observer
> instances?
>

It is good to see that you finally acknowledge that your theory is not
quantum mechanics.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

Le lun. 24 févr. 2025, 23:29, Bruce Kellett  a
écrit :

> On Tue, Feb 25, 2025 at 9:15 AM Quentin Anciaux 
> wrote:
>
>>
>> You keep assuming that one branch corresponds to one observer, but that’s
>> simply not what MWI proposes.
>>
>
> That is exactly what Everett (MWI) proposes. Have you not in the least
> understood what I have been saying. On each measurement of the binary
> wavefunction, the observer splits, so that there is one copy on each
> branch. Continuing this process N times leads to the 2^N branches with one
> observer on each sequence. There is only one observer per sequence
> (branch), because that is what the unitary splitting process gives you.
>
>
> Everett’s framework is about relative states, not discrete worlds with
>> single, isolated observers. If you treat branches as coarse-grained
>> partitions of an underlying continuous wavefunction, then observer
>> instances scale with amplitude,
>>
>
> But that is not what unitary evolution and the Schrodinger equation say.
> It is just pure fantasy on your part. I can ask, where do these additional
> observers on each branch come from? They are not included in any of the
> mathematics of unitary evolution.
>

Bruce,

If we consider that there is always an infinite superposition of branches,
then each partition also contains an infinite number of branches, but with
different relative measures. The key point is that branches are not
discrete objects—they are coarse-grained regions of the wavefunction shaped
by decoherence.

Unitary evolution does not create additional observers explicitly, but if
measure reflects the density of observer instances within the wavefunction,
then the number of observers experiencing a particular sequence is not
uniform across all branches. This avoids naive branch counting and aligns
with how probabilities emerge from continuous distributions rather than
discrete events.

The challenge is formalizing this within unitary QM, possibly through
information-theoretic approaches, measure theory, or even constraints from
computational complexity. If amplitudes guide the structure of the
wavefunction, why wouldn’t they also influence the distribution of observer
instances?

Quentin


> and that’s what leads to the Born rule. The fact that all 2^N sequences
>> exist doesn’t mean they contain the same number of observer copies. If you
>> disagree, you need to justify why unitary evolution should produce equal
>> weighting when the amplitudes explicitly define the structure of the
>> wavefunction.
>>
>
> That is what has been done. Unitary evolution produces one observer for
> each branch, because the observers are copies that arise from unitary
> splits according to the Schrodinger equation. At this stage, there are no
> such things as branch weights, because they have not been defined. I am
> just following unitary evolution and, although the amplitudes get carried
> along, they have no particular meaning or significance until some such is
> imposed from outside.
>
> Bruce
>
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

Your response assumes that unitary evolution inherently produces "one
observer per branch" in a discrete way, but that’s not what follows from
the wavefunction’s continuous structure. Everett’s relative state
formulation does not propose discrete worlds but rather an evolving
superposition where decoherence prevents interference. The fact that we
describe macroscopic branches as "splitting" is a convenient approximation,
not a fundamental aspect of the theory.

The key point you keep ignoring is that amplitudes are not just "carried
along" without meaning—they define the structure of the wavefunction, and
decoherence prevents low-amplitude branches from significantly contributing
to observer experiences. Your claim that "one observer per branch" follows
directly from unitary evolution is an assumption, not a derivation.

If you insist that unitary evolution cannot produce probability weights,
then your argument applies equally to any interpretation of quantum
mechanics. The Born rule is a fact of experiment, and any valid
interpretation must explain it. If you believe MWI cannot do so, you must
show why—not just assert that it "hasn’t been done" while dismissing
attempts to derive it. Assume your pride, publish and get the glory.

Quentin

Le lun. 24 févr. 2025, 23:29, Bruce Kellett  a
écrit :

> On Tue, Feb 25, 2025 at 9:15 AM Quentin Anciaux 
> wrote:
>
>>
>> You keep assuming that one branch corresponds to one observer, but that’s
>> simply not what MWI proposes.
>>
>
> That is exactly what Everett (MWI) proposes. Have you not in the least
> understood what I have been saying. On each measurement of the binary
> wavefunction, the observer splits, so that there is one copy on each
> branch. Continuing this process N times leads to the 2^N branches with one
> observer on each sequence. There is only one observer per sequence
> (branch), because that is what the unitary splitting process gives you.
>
>
> Everett’s framework is about relative states, not discrete worlds with
>> single, isolated observers. If you treat branches as coarse-grained
>> partitions of an underlying continuous wavefunction, then observer
>> instances scale with amplitude,
>>
>
> But that is not what unitary evolution and the Schrodinger equation say.
> It is just pure fantasy on your part. I can ask, where do these additional
> observers on each branch come from? They are not included in any of the
> mathematics of unitary evolution.
>
> and that’s what leads to the Born rule. The fact that all 2^N sequences
>> exist doesn’t mean they contain the same number of observer copies. If you
>> disagree, you need to justify why unitary evolution should produce equal
>> weighting when the amplitudes explicitly define the structure of the
>> wavefunction.
>>
>
> That is what has been done. Unitary evolution produces one observer for
> each branch, because the observers are copies that arise from unitary
> splits according to the Schrodinger equation. At this stage, there are no
> such things as branch weights, because they have not been defined. I am
> just following unitary evolution and, although the amplitudes get carried
> along, they have no particular meaning or significance until some such is
> imposed from outside.
>
> Bruce
>
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/24/2025 9:51 AM, John Clark wrote:



On Sun, Feb 23, 2025 at 6:55 PM Brent Meeker  
wrote:


*>> the observer himself must also obey Schrodinger's
equation, not just the thing he is trying to predict. So there
is no alternative but to resort to probability. *


/> No, that can't be the fundamental reason.  The HUP doesn't
derive from the quantum nature of measuring devices. /


* If Schrodinger's equation is correct, which is to say if Many Worlds 
is correct, then both observations have been made in the Multiverse, 
but not by the same observer.*

A statement you make with no evidence for it.

Schroedinger's equation + Born rule has worked just fine in a one world 
interpretation.  So MWI is not logically implied by their success.


/> SG experiment results don't depend on quantum aspects of the
apparatus./


*Of course it does!The electron is in a superposition of spin up and 
spin down state, and the SG device is in a superposition of having 
detected spin up and detected spin down state, and the human observer 
is in a superposition of "having seen the SG device being in the spin 
up state and in the spin down state. You are making the assumption 
that the Heisenberg cut exists, Many Worlds has no need of that 
assumption.

*
No, I'm noticing that the quantum character of the SG device has nothing 
to do with your supposed splitting.  It is only necessary that it 
register the spin state.


/> //Zurek proposes that there must be another effect,
"envariance", whereby interaction with the environment must select
only certain a bases which survive decoherence./


*Zurek’s "envariance" means that if a system is  entangled with its 
environment then  mathematics insists we assign equal probabilities to 
outcomes in which the amplitudes in the quantum state’s expansion are 
equal, and obviously the squared magnitudes of the amplitudes. And I 
don't need to tell you what that leads to.*
That's not "envariance".  Envariance is Zurek's proposal for how the 
preferred basis problem should be solved.  I guess I did need to tell 
you that.

*
*
* Completely independent of Hugh Everett, string theory says that 
there are 10^600 different ways 7 additional spatial dimensions can be 
shrunk down and interlaced with each other with each of the 10^600 
leading to a different universe. And independent of both Everett and 
string theory, Alan Guth's theory of cosmic inflation along with 
Andrei Linde's "eternal inflation" which explains why inflation ever 
stops, leads to the conclusion that there must be even more universes, 
perhaps even an infinite number of them not just an astronomical number. *
But string theory and eternal inflation don't postulate things that are 
unobservable /by construction./


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-24 Thread Bruce Kellett

On Tue, Feb 25, 2025 at 9:15 AM Quentin Anciaux  wrote:

>
> You keep assuming that one branch corresponds to one observer, but that’s
> simply not what MWI proposes.
>

That is exactly what Everett (MWI) proposes. Have you not in the least
understood what I have been saying. On each measurement of the binary
wavefunction, the observer splits, so that there is one copy on each
branch. Continuing this process N times leads to the 2^N branches with one
observer on each sequence. There is only one observer per sequence
(branch), because that is what the unitary splitting process gives you.

Everett’s framework is about relative states, not discrete worlds with
> single, isolated observers. If you treat branches as coarse-grained
> partitions of an underlying continuous wavefunction, then observer
> instances scale with amplitude,
>

But that is not what unitary evolution and the Schrodinger equation say. It
is just pure fantasy on your part. I can ask, where do these additional
observers on each branch come from? They are not included in any of the
mathematics of unitary evolution.

and that’s what leads to the Born rule. The fact that all 2^N sequences
> exist doesn’t mean they contain the same number of observer copies. If you
> disagree, you need to justify why unitary evolution should produce equal
> weighting when the amplitudes explicitly define the structure of the
> wavefunction.
>

That is what has been done. Unitary evolution produces one observer for
each branch, because the observers are copies that arise from unitary
splits according to the Schrodinger equation. At this stage, there are no
such things as branch weights, because they have not been defined. I am
just following unitary evolution and, although the amplitudes get carried
along, they have no particular meaning or significance until some such is
imposed from outside.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/24/2025 1:07 PM, Quentin Anciaux wrote:

Brent,

The issue is precisely that if you start with only unitary evolution 
and no additional assumptions, you don’t get probabilities at all—just 
a deterministic wavefunction. That’s why the Born rule must be 
explained rather than assumed. The problem is not that MWI contradicts 
the Born rule, but that it needs to derive it without assuming it.


Your argument boils down to saying, "The Born rule is empirically 
confirmed, so MWI must explicitly postulate it."
No, you leave out the point that the Born rule can't be derived from 
just the Schroedinger equation.  As Bruce as explained repeatedly, MWI 
alone provides no mechanism for changing the sequences generated by 
measurements.  You are of course free to postulate a probability measure 
based on the wave-function amplitudes...which is assuming the Born 
rule.  It's what everybody did for 40yrs before Everett wrote his paper 
and which everybody has continued doing sense.



But any interpretation of QM, including single-world ones, requires 
some justification for why the squared amplitude determines 
probability. If MWI needs additional reasoning to get there, that’s an 
open question, not a refutation.
What if you can't get there from bare MWI?  Many have tried and failed.  
Why not just accept that it's a probabilistic rule that needs to be 
added to the interpretation.  Gleason's theorem shows that there's no 
other way to apply a probabilistic measure if there are more than two 
possible results.  Although  Gleason's theorem is independent of choice 
of basis, so there's still the preferred basis problem; which we hope 
decoherence can solve but I don't think anyone has shown it yet.





You say that different values of a and b still produce the same 
sequences, but What you’re missing is that in MWI, observer instances 
are not evenly distributed across all sequences—this is fundamental to 
Everett’s relative state interpretation. If all sequences contributed 
equally, there would be no need for measure at all, and MWI would have 
been dismissed from the start. Everett’s entire motivation was to 
account for probability within a deterministic framework, meaning your 
argument misrepresents what MWI actually proposes. The number of 
observer instances experiencing each sequence scales with the 
amplitude squared
But that doesn't follow from the measurements which just produce one 
branch for every possible result.  It only follows from assuming the 
branches have a probability measure equal to the square modulus of the 
amplitude, aka the Born rule.  The concept of "observer instances" and 
their "experiences" is a fantasy.  The number of observers of a 
particular result can be anything once the result in recorded.


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

Le lun. 24 févr. 2025, 23:09, Brent Meeker  a écrit :

>
>
> On 2/24/2025 1:07 PM, Quentin Anciaux wrote:
>
> Brent,
>
> The issue is precisely that if you start with only unitary evolution and
> no additional assumptions, you don’t get probabilities at all—just a
> deterministic wavefunction. That’s why the Born rule must be explained
> rather than assumed. The problem is not that MWI contradicts the Born rule,
> but that it needs to derive it without assuming it.
>
> Your argument boils down to saying, "The Born rule is empirically
> confirmed, so MWI must explicitly postulate it."
>
> No, you leave out the point that the Born rule can't be derived from just
> the Schroedinger equation.  As Bruce as explained repeatedly, MWI alone
> provides no mechanism for changing the sequences generated by
> measurements.  You are of course free to postulate a probability measure
> based on the wave-function amplitudes...which is assuming the Born rule.
> It's what everybody did for 40yrs before Everett wrote his paper and which
> everybody has continued doing sense.
>
>
> But any interpretation of QM, including single-world ones, requires some
> justification for why the squared amplitude determines probability. If MWI
> needs additional reasoning to get there, that’s an open question, not a
> refutation.
>
> What if you can't get there from bare MWI?  Many have tried and failed.
> Why not just accept that it's a probabilistic rule that needs to be added
> to the interpretation.  Gleason's theorem shows that there's no other way
> to apply a probabilistic measure if there are more than two possible
> results.  Although  Gleason's theorem is independent of choice of basis, so
> there's still the preferred basis problem; which we hope decoherence can
> solve but I don't think anyone has shown it yet.
>
>
>
> You say that different values of a and b still produce the same sequences,
> but What you’re missing is that in MWI, observer instances are not evenly
> distributed across all sequences—this is fundamental to Everett’s relative
> state interpretation. If all sequences contributed equally, there would be
> no need for measure at all, and MWI would have been dismissed from the
> start. Everett’s entire motivation was to account for probability within a
> deterministic framework, meaning your argument misrepresents what MWI
> actually proposes. The number of observer instances experiencing each
> sequence scales with the amplitude squared
>
> But that doesn't follow from the measurements which just produce one
> branch for every possible result.  It only follows from assuming the
> branches have a probability measure equal to the square modulus of the
> amplitude, aka the Born rule.  The concept of "observer instances" and
> their "experiences" is a fantasy.  The number of observers of a particular
> result can be anything once the result in recorded.
>
> Brent
>

You keep assuming that one branch corresponds to one observer, but that’s
simply not what MWI proposes. Everett’s framework is about relative states,
not discrete worlds with single, isolated observers. If you treat branches
as coarse-grained partitions of an underlying continuous wavefunction, then
observer instances scale with amplitude, and that’s what leads to the Born
rule. The fact that all 2^N sequences exist doesn’t mean they contain the
same number of observer copies. If you disagree, you need to justify why
unitary evolution should produce equal weighting when the amplitudes
explicitly define the structure of the wavefunction.

Quentin

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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

The issue is precisely that if you start with only unitary evolution and no
additional assumptions, you don’t get probabilities at all—just a
deterministic wavefunction. That’s why the Born rule must be explained
rather than assumed. The problem is not that MWI contradicts the Born rule,
but that it needs to derive it without assuming it.

Your argument boils down to saying, "The Born rule is empirically
confirmed, so MWI must explicitly postulate it." But any interpretation of
QM, including single-world ones, requires some justification for why the
squared amplitude determines probability. If MWI needs additional reasoning
to get there, that’s an open question, not a refutation.

You say that different values of a and b still produce the same sequences,
but What you’re missing is that in MWI, observer instances are not evenly
distributed across all sequences—this is fundamental to Everett’s relative
state interpretation. If all sequences contributed equally, there would be
no need for measure at all, and MWI would have been dismissed from the
start. Everett’s entire motivation was to account for probability within a
deterministic framework, meaning your argument misrepresents what MWI
actually proposes. The number of observer instances experiencing each
sequence scales with the amplitude squared, so the observed frequencies
match the Born rule. This is not an arbitrary postulate—it follows from the
way measure is assigned in the wavefunction.

If you believe this is just "counting branches," you are assuming that all
branches have equal weight, which is exactly what’s in question. The fact
that small N allows some spread in observed averages is true in any
probabilistic system—classical or quantum—but that does not mean the
amplitudes are irrelevant to observer statistics.

Ultimately, the challenge is not proving the Born rule holds empirically—we
know it does. The question is whether it emerges naturally from unitary
evolution or must be separately assumed. Simply asserting that MWI "doesn’t
work without the Born rule" is not an argument—it’s a restatement of the
problem.

Quentin

Le lun. 24 févr. 2025, 21:43, Brent Meeker  a écrit :

>
>
> On 2/24/2025 3:07 AM, Quentin Anciaux wrote:
>
> Bruce,
>
> Your argument still assumes what it wants to prove. Yes, the 2^N sequences
> exist independently of the amplitudes, but the claim that they all
> contribute equally to probability remains an implicit assumption in your
> reasoning. The fact that the sequences themselves don’t depend on a and b
> does not mean that their statistical weights—how often an observer finds
> themselves in each sequence—are independent of amplitudes.
>
> Which means you need some different, separate theory about how "observer
> distribution" is determined in a way that depends on the amplitudes.
>
>
> Your core mistake is treating the observed sequences as primary while
> ignoring the fact that the number of observer instances experiencing each
> sequence is what matters. The amplitudes determine the measure of each
> branch, meaning the vast majority of observers end up in sequences that
> follow the Born rule.
>
> Not necessarily a "vast majority".  For a short sequence, small N, there
> should be a lot of spread in the observed average.  Only for large N does
> the distribution become sharply peaked.  "Follow the Born rule" is a little
> ambiguous since it's probabilitistic.  "Consistent with the Born rule" is
> better.
>
> You are simply assuming that observer distribution is uniform across
> sequences, which contradicts the entire structure of quantum mechanics.
>
> You mean it doesn't comport with the Born rule...and the Born rule is
> empirically confirmed...which is the whole point.  The Born rule must be
> invoked to assign numbers of observers, aka probabilities, to the 2^N
> sequences.
>
>
> You keep insisting that different values of a and b still produce the same
> sequences. Yes, the sequences are the same in a mathematical sense, but
> that does not mean they are observed with equal frequency. This is like
> saying that rolling a biased die produces the same possible numbers as a
> fair die and then concluding that all outcomes are equally likely. The
> actual distribution of observed frequencies follows the amplitudes squared,
> as the Born rule predicts.
>
> If you believe MWI contradicts the Born rule,
>
> It doesn't contradict it unless you take it as the whole of the theory,
> without the Born rule.  If you don't include the Born rule, or an
> equivalent postulate, then you are left with nothing but counting the
> branches, which doesn't work for a=/=b.
>
> Brent
>
>
> publish a formal proof. Otherwise, repeating the same flawed argument does
> not make it more correct.
>
> Quentin
>
>
>
> Le lun. 24 févr. 2025, 11:49, Bruce Kellett  a
> écrit :
>
>> On Mon, Feb 24, 2025 at 5:31 PM Quentin Anciaux 
>> wrote:
>>
>>> Bruce,
>>>
>>> Your assertion is absurd. The existence of 2^N sequences is not in
>>> q

Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/24/2025 3:07 AM, Quentin Anciaux wrote:

Bruce,

Your argument still assumes what it wants to prove. Yes, the 2^N 
sequences exist independently of the amplitudes, but the claim that 
they all contribute equally to probability remains an implicit 
assumption in your reasoning. The fact that the sequences themselves 
don’t depend on a and b does not mean that their statistical 
weights—how often an observer finds themselves in each sequence—are 
independent of amplitudes.
Which means you need some different, separate theory about how "observer 
distribution" is determined in a way that depends on the amplitudes.


Your core mistake is treating the observed sequences as primary while 
ignoring the fact that the number of observer instances experiencing 
each sequence is what matters. The amplitudes determine the measure of 
each branch, meaning the vast majority of observers end up in 
sequences that follow the Born rule.
Not necessarily a "vast majority".  For a short sequence, small N, there 
should be a lot of spread in the observed average.  Only for large N 
does the distribution become sharply peaked.  "Follow the Born rule" is 
a little ambiguous since it's probabilitistic. "Consistent with the Born 
rule" is better.


You are simply assuming that observer distribution is uniform across 
sequences, which contradicts the entire structure of quantum mechanics.
You mean it doesn't comport with the Born rule...and the Born rule is 
empirically confirmed...which is the whole point.  The Born rule must be 
invoked to assign numbers of observers, aka probabilities, to the 2^N 
sequences.


You keep insisting that different values of a and b still produce the 
same sequences. Yes, the sequences are the same in a mathematical 
sense, but that does not mean they are observed with equal frequency. 
This is like saying that rolling a biased die produces the same 
possible numbers as a fair die and then concluding that all outcomes 
are equally likely. The actual distribution of observed frequencies 
follows the amplitudes squared, as the Born rule predicts.


If you believe MWI contradicts the Born rule,
It doesn't contradict it unless you take it as the whole of the theory, 
without the Born rule.  If you don't include the Born rule, or an 
equivalent postulate, then you are left with nothing but counting the 
branches, which doesn't work for a=/=b.


Brent


publish a formal proof. Otherwise, repeating the same flawed argument 
does not make it more correct.


Quentin



Le lun. 24 févr. 2025, 11:49, Bruce Kellett  a 
écrit :


On Mon, Feb 24, 2025 at 5:31 PM Quentin Anciaux
 wrote:

Bruce,

Your assertion is absurd. The existence of 2^N sequences is
not in question—it's a direct prediction of MWI. The issue is
whether all sequences contribute equally to probability, which
they demonstrably do not, as experiments confirm the Born
rule, not a uniform distribution.


You are persisting with this idea that my argument is that all the
2^N "sequences contribute equally to probability". But I have
never made any such claim, and such an idea is completely beside
the point. The first important point comes after I mention the 2^N
binary sequences. I point out that these come from the binary
state a|0> + b|1>, but the sequences themselves are independent of
the amplitudes a and b. This means that if you repeat N trials
with different amplitudes a and b, you will get exactly the same
2^N sequences. The point of this is that the amplitudes themselves
play no role in the formation of the experimentally observed
binary sequences.

You must remember that the sequences of UP and DOWN (or zero and
one in my coding) are the data that any experimentalist measuring 
the spin projections of N spin-half atoms will get. They are the
data he/she will work with, and that data is independent of the
amplitudes.

The second point is that from that experimental data, the
experimentalist can get an estimate of the probability of
obtaining a zero. Say there are r zeros in someone's observed
sequence. Then a good estimate of the probability of getting a
zero will be p =  r/N. If one compares this with the Born rule
prediction, which is |a|^2, then in the majority of cases the
experimentalist will find the Born rule to be disconfirmed: his
estimate p = r/N will not equal |a|^2. Since the same applies for
any sequence in the set of 2^N:  the value of r for different
experimentalists, will range from zero to one. But all have the
same Born rule probability, |a|^2. This is what happens when the
data from such an experiment is used for theory confirmation. MWI
is not confirmed, whereas the single world model is confirmed on
every occasion.

The problem is made more acute if you consider that we can take
completely different values for the amplitudes a and b,

Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-24 Thread John Clark

On Sun, Feb 23, 2025 at 6:55 PM Brent Meeker  wrote:

*>> the observer himself must also obey Schrodinger's equation, not just
>> the thing he is trying to predict. So there is no alternative but to resort
>> to probability. *
>
>
> *> No, that can't be the fundamental reason.  The HUP doesn't derive from
> the quantum nature of measuring devices. *
>

*We're repeating stuff we've already argued about. On January 10 I said the
following and I still stand behind it and see no reason to change it: *

 *"If Quantum Mechanics is correct, and I think it's a pretty damn good
assumption that it is, then in the Schrodinger cat experiment you've got a
superposition of 2 quantum states,  { [ ( a live cat) + (the environment
with a live cat in it) + (Brent Meeker in that environment looking at a
live cat) ]  +  [ ( a dead cat) + (the environment with a dead cat in it) +
(Brent Meeker in that environment looking at a dead cat)] }. Thus Brent
Meeker#1 would say it is an observable fact that the cat is alive and Brent
Meeker#2 would say it is an observable fact that the cat is not alive."*

*The best rebuttal to that you were able to come up with was "And only one
of #1 or #2 has ever been observed", but of course you just made that
statement and provided no evidence that that is indeed the case. If
Schrodinger's equation is correct, which is to say if Many Worlds is
correct, then both observations have been made in the Multiverse, but not
by the same observer. *

> *> SG experiment results don't depend on quantum aspects of the apparatus.*
>

*Of course it does! The electron is in a superposition of spin up and spin
down state, and the SG device is in a superposition of having detected spin
up and detected spin down state, and the human observer is in a
superposition of "having seen the SG device being in the spin up state and
in the spin down state.  You are making the assumption that the Heisenberg
cut exists, Many Worlds has no need of that assumption. *

> *> **Zurek proposes that there must be another effect, "envariance",
> whereby interaction with the environment must select only certain a bases
> which survive decoherence.*
>

*Zurek’s "envariance" means that if a system is  entangled with its
environment then  mathematics insists we assign equal probabilities to
outcomes in which the amplitudes in the quantum state’s expansion are
equal, and obviously the squared magnitudes of the amplitudes. And I don't
need to tell you what that leads to.*

*Wojciech Zurek says he does not have a favorite quantum interpretation and
remains neutral, although his work is compatible with many worlds, and he
does say that the superposition principle is universally applicable and
that interpretations like MWI refuse to draw a quantum-classical boundary,
there is no "Heisenberg cut". *

> *>>No, not if the complex wave is 3-D or higher.*
>>
>

>>Yes, that's Gleason's theorem.
>
>
*Exactly.  *

*> It's not 4-D.  It's 4N-D where N is the number of particles.*
>

*True, but that just makes my case even stronger*

>> *>> What should a rational observer do if he wants to make bets about the
>> future? **Follow the Born Rule.*
>
>
> *> Which as I've noted depends on MORE than "Just the Schroedinger
> equation.*
>

*I would maintain that if you have Schrödinger's equation and Gleason's
theorem then, provided you do NOT make the assumption that hidden variables
exist (and because  Bell's Inequality is violated we know for a fact that
if they do exist they can't be local). And if you do NOT make the
assumption that everyday probability is wrong because the probability
measure of mutually exclusive outcomes occurring is NOT additive. But do
you really want to make that assumption? If you do then you'd have to
conclude that the probability of a coin coming up heads or tails is NOT
equal to the probability of it coming up heads plus the probability of it
coming up tails.*

*It's interesting that Hugh Everett's explanation of why probability is
necessary even though Schrodinger's equation is deterministic is NOT the
only thing leading to the conclusion that the single universe idea must be
wrong. Completely independent of Hugh Everett, string theory says that
there are 10^600 different ways 7 additional spatial dimensions can be
shrunk down and interlaced with each other with each of the 10^600 leading
to a different universe. And independent of both Everett and string theory,
Alan Guth's theory of cosmic inflation along with Andrei Linde's "eternal
inflation" which explains why inflation ever stops, leads to the conclusion
that there must be even more universes, perhaps even an infinite number of
them not just an astronomical number. *

*   John K ClarkSee what's on my new list at  Extropolis
*
plb

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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

Your argument still assumes what it wants to prove. Yes, the 2^N sequences
exist independently of the amplitudes, but the claim that they all
contribute equally to probability remains an implicit assumption in your
reasoning. The fact that the sequences themselves don’t depend on a and b
does not mean that their statistical weights—how often an observer finds
themselves in each sequence—are independent of amplitudes.

Your core mistake is treating the observed sequences as primary while
ignoring the fact that the number of observer instances experiencing each
sequence is what matters. The amplitudes determine the measure of each
branch, meaning the vast majority of observers end up in sequences that
follow the Born rule. You are simply assuming that observer distribution is
uniform across sequences, which contradicts the entire structure of quantum
mechanics.

You keep insisting that different values of a and b still produce the same
sequences. Yes, the sequences are the same in a mathematical sense, but
that does not mean they are observed with equal frequency. This is like
saying that rolling a biased die produces the same possible numbers as a
fair die and then concluding that all outcomes are equally likely. The
actual distribution of observed frequencies follows the amplitudes squared,
as the Born rule predicts.

If you believe MWI contradicts the Born rule, publish a formal proof.
Otherwise, repeating the same flawed argument does not make it more correct.

Quentin

Le lun. 24 févr. 2025, 11:49, Bruce Kellett  a
écrit :

> On Mon, Feb 24, 2025 at 5:31 PM Quentin Anciaux 
> wrote:
>
>> Bruce,
>>
>> Your assertion is absurd. The existence of 2^N sequences is not in
>> question—it's a direct prediction of MWI. The issue is whether all
>> sequences contribute equally to probability, which they demonstrably do
>> not, as experiments confirm the Born rule, not a uniform distribution.
>>
>
> You are persisting with this idea that my argument is that all the 2^N
> "sequences contribute equally to probability". But I have never made any
> such claim, and such an idea is completely beside the point. The first
> important point comes after I mention the 2^N binary sequences. I point out
> that these come from the binary state a|0> + b|1>, but the sequences
> themselves are independent of the amplitudes a and b. This means that if
> you repeat N trials with different amplitudes a and b, you will get exactly
> the same 2^N sequences. The point of this is that the amplitudes themselves
> play no role in the formation of the experimentally observed binary
> sequences.
>
> You must remember that the sequences of UP and DOWN (or zero and one in my
> coding) are the data that any experimentalist measuring  the spin
> projections of N spin-half atoms will get. They are the data he/she will
> work with, and that data is independent of the amplitudes.
>
> The second point is that from that experimental data, the experimentalist
> can get an estimate of the probability of obtaining a zero. Say there are r
> zeros in someone's observed sequence. Then a good estimate of the
> probability of getting a zero will be p =  r/N. If one compares this with
> the Born rule prediction, which is |a|^2, then in the majority of cases the
> experimentalist will find the Born rule to be disconfirmed: his estimate p
> = r/N will not equal |a|^2. Since the same applies for any sequence in the
> set of 2^N:  the value of r for different experimentalists, will range from
> zero to one. But all have the same Born rule probability, |a|^2. This is
> what happens when the data from such an experiment is used for theory
> confirmation. MWI is not confirmed, whereas the single world model is
> confirmed on every occasion.
>
> The problem is made more acute if you consider that we can take completely
> different values for the amplitudes a and b, but we will get the same
> sequences, and the same set of values of p = r/N, even though the Born
> probabilities |a|^2 are wildly different. Of course, there is a value of r
> in the set of sequences that agrees with the Born probability, simply
> because the set of sequences covers all possibilities, including the set of
> zeros and ones that would be obtained by a single experimentalist in a
> single world scenario. In the single world, the Born rule is confirmed in
> every case, Though in the many-world case, the majority of experimentalists
> will find that the Born rule is violated.
>
> Bruce
>
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> email to everything-list+unsubscr...@googlegroups.com.
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>

Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-24 Thread Bruce Kellett

On Mon, Feb 24, 2025 at 5:31 PM Quentin Anciaux  wrote:

> Bruce,
>
> Your assertion is absurd. The existence of 2^N sequences is not in
> question—it's a direct prediction of MWI. The issue is whether all
> sequences contribute equally to probability, which they demonstrably do
> not, as experiments confirm the Born rule, not a uniform distribution.
>

You are persisting with this idea that my argument is that all the 2^N
"sequences contribute equally to probability". But I have never made any
such claim, and such an idea is completely beside the point. The first
important point comes after I mention the 2^N binary sequences. I point out
that these come from the binary state a|0> + b|1>, but the sequences
themselves are independent of the amplitudes a and b. This means that if
you repeat N trials with different amplitudes a and b, you will get exactly
the same 2^N sequences. The point of this is that the amplitudes themselves
play no role in the formation of the experimentally observed binary
sequences.

You must remember that the sequences of UP and DOWN (or zero and one in my
coding) are the data that any experimentalist measuring  the spin
projections of N spin-half atoms will get. They are the data he/she will
work with, and that data is independent of the amplitudes.

The second point is that from that experimental data, the experimentalist
can get an estimate of the probability of obtaining a zero. Say there are r
zeros in someone's observed sequence. Then a good estimate of the
probability of getting a zero will be p =  r/N. If one compares this with
the Born rule prediction, which is |a|^2, then in the majority of cases the
experimentalist will find the Born rule to be disconfirmed: his estimate p
= r/N will not equal |a|^2. Since the same applies for any sequence in the
set of 2^N:  the value of r for different experimentalists, will range from
zero to one. But all have the same Born rule probability, |a|^2. This is
what happens when the data from such an experiment is used for theory
confirmation. MWI is not confirmed, whereas the single world model is
confirmed on every occasion.

The problem is made more acute if you consider that we can take completely
different values for the amplitudes a and b, but we will get the same
sequences, and the same set of values of p = r/N, even though the Born
probabilities |a|^2 are wildly different. Of course, there is a value of r
in the set of sequences that agrees with the Born probability, simply
because the set of sequences covers all possibilities, including the set of
zeros and ones that would be obtained by a single experimentalist in a
single world scenario. In the single world, the Born rule is confirmed in
every case, Though in the many-world case, the majority of experimentalists
will find that the Born rule is violated.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-23 Thread Quentin Anciaux

Bruce,

Your assertion is absurd. The existence of 2^N sequences is not in
question—it's a direct prediction of MWI. The issue is whether all
sequences contribute equally to probability, which they demonstrably do
not, as experiments confirm the Born rule, not a uniform distribution.

I’ve already provided multiple counterexamples—the lottery analogy,
asymmetric duplication, and multiple instances of a conscious program—all
illustrating why raw sequence count is irrelevant without considering
measure. Amplitudes are fundamental in the Schrödinger equation, and
treating them as meaningless contradicts everything we know about quantum
mechanics.

If you believe you’ve disproven MWI, publish it. Otherwise, all you’re
doing is repeating claims without engaging with their refutation.

Quentin

Le dim. 23 févr. 2025, 23:22, Bruce Kellett  a
écrit :

> On Mon, Feb 24, 2025 at 9:00 AM Quentin Anciaux 
> wrote:
>
>> Bruce, you keep insisting that unitary QM provides no mechanism for
>> measure affecting observer distribution, but you haven't actually proven
>> this—only asserted it.
>>
>
> You have not proven the contrary. It is all merely assertion on your part.
> If you are so convinced that unitary evolution can produce the structures
> you envisage, then derive those structures with the context of unitary QM.
> Show the mathematics!
>
> All that is required to prove my point is to observer that the 2^N binary
> sequences that result from repeated measurements of the simple binary state
> a|0> + b|1> do not depend on the amplitudes a and b. If you dispute this,
> show how the binary sequences do depend on the amplitudes. Don't just
> assert it. What different set of sequences do I get with differing values
> of a and b?
>
> Bruce
>
> --
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-23 Thread Brent Meeker

On 2/23/2025 5:41 AM, John Clark wrote:
On Sat, Feb 22, 2025 at 7:00 PM Brent Meeker
wrote:

*>> You're just repeating the definition of the Born Rule, and
everyone agrees it works, but some of us would like to know
WHY it works and WHY it's even necessary given the fact that
Schrodinger's equation is deterministic *

/> Well if you don't think it's "necessary"/

*Don't be ridiculous!I said the Born Rule was necessary. What I asked
is _WHY_ is it necessary? *

/> science can only answer "why" questions if there is some more
fundamental theory on which to base the answer. /

*And that theory was introduced by Hugh Everett in 1957 and improved
by Sean Carroll and David Deutsch and many many others over the last
68 years. *

> /just taking Schroedinger's equation as the basis is not
sufficient. So it clashes with the MWI mantra of "Just the
Schroedinger equation/

*Everybody agrees that Schrodinger's equation works, and everybody
agrees it says something about what is going on at the deepest level
of reality, but some believe it can't be the entire story and there
must be something more that was happening. Many Worlds asks us to
imagine what would be the result if there was _NOT_ something more
going on and it was just Schrodinger's equation.*

*Would an observer have enough information to make a prediction with
an arbitrary level of precision?*

*
No, and the fundamental reason why is that the observer himself must
also obey Schrodinger's equation, not just the thing he is trying to
predict. So there is no alternative but to resort to probability. *
No, that can't be the fundamental reason. The HUP doesn't derive from
the quantum nature of measuring devices. SG experiment results don't
depend on quantum aspects of the apparatus. And predictions of 0 vs. 1
results don't require arbitrary levels of precision.

*Is there a way to get a real number out of the complex 4-D wave that
the equation produces such that it's always between 0 and 1 and the
probabilities always add up to exactly 1?

It's not 4-D. It's 4N-D where N is the number of particles.

*
*
*Yes, take the absolute value of the wave function and then square it.*

And normalize it to 1.

*Mathematically is there another way to produce a set of numbers from
Schrodinger's wave that have the properties that a probability must have?

*
Normalizing the squared modulus make it's value 1. What other numbers
it gives you depends on the assumed basis states. Which is why Zurek
proposes that there must be another effect, "envariance", whereby
interaction with the environment must select only certain a bases which
survive decoherence.

*
No, not if the complex wave is 3-D or higher.*

Yes, that's Gleason's theorem.

*
*
*What should a rational observer do if he wants to make bets about the
future? *

*
*
*Follow the Born Rule.
*

Which as I've noted depends on MORE than "Just the Schroedinger equation."

Brent*
*

*
*
*John K Clark See what's on my new list at Extropolis
*

dx5

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-23 Thread Bruce Kellett

On Mon, Feb 24, 2025 at 9:00 AM Quentin Anciaux  wrote:

> Bruce, you keep insisting that unitary QM provides no mechanism for
> measure affecting observer distribution, but you haven't actually proven
> this—only asserted it.
>

You have not proven the contrary. It is all merely assertion on your part.
If you are so convinced that unitary evolution can produce the structures
you envisage, then derive those structures with the context of unitary QM.
Show the mathematics!

All that is required to prove my point is to observer that the 2^N binary
sequences that result from repeated measurements of the simple binary state
a|0> + b|1> do not depend on the amplitudes a and b. If you dispute this,
show how the binary sequences do depend on the amplitudes. Don't just
assert it. What different set of sequences do I get with differing values
of a and b?

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-23 Thread Quentin Anciaux

Bruce, you keep insisting that unitary QM provides no mechanism for measure
affecting observer distribution, but you haven't actually proven this—only
asserted it. If you're so certain, I encourage you to publish your
refutation of MWI and get the recognition you deserve. Otherwise, repeating
that it 'doesn’t work' without engaging with alternative formulations is
just dogmatism.

Quentin

Le dim. 23 févr. 2025, 22:33, Bruce Kellett  a
écrit :

> On Sun, Feb 23, 2025 at 6:17 PM Quentin Anciaux 
> wrote:
>
>>
>> You’re treating "branches" as isolated, discrete units, but if the
>> wavefunction remains a continuous superposition, then what we call "a
>> branch" is just an approximation—a macroscopic coarse-graining of many
>> micro-branches. Decoherence prevents interference between them, but it does
>> not imply a strict one-to-one mapping between observer instances and
>> branches.
>>
>
> Unitary decoherence does not work as you claim.
>
> If more observer instances exist in a high-amplitude region of the
>> wavefunction, then an observer randomly drawn from the total set of
>> observers is overwhelmingly likely to experience a sequence in proportion
>> to its measure, not because the sequence itself is somehow weighted, but
>> because there are simply more instances of the observer experiencing it.
>>
>
> There is no mechanism in unitary quantum mechanics that can give the
> structure that you envisage.
>
> This is not just an abstract claim—it follows directly from how measure
>> works in probability. If you duplicate a computational process a million
>> times and run it on different hardware, the subjective experience of that
>> process does not exist in just one instance. Similarly, in MWI, if
>> decoherence results in more observer instances in a high-measure region,
>> then most self-locating observers will find themselves in those regions.
>>
>
> That does not work in unitary quantum mechanics.
>
> Bruce
>
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-23 Thread Bruce Kellett

On Sun, Feb 23, 2025 at 6:17 PM Quentin Anciaux  wrote:

>
> You’re treating "branches" as isolated, discrete units, but if the
> wavefunction remains a continuous superposition, then what we call "a
> branch" is just an approximation—a macroscopic coarse-graining of many
> micro-branches. Decoherence prevents interference between them, but it does
> not imply a strict one-to-one mapping between observer instances and
> branches.
>

Unitary decoherence does not work as you claim.

If more observer instances exist in a high-amplitude region of the
> wavefunction, then an observer randomly drawn from the total set of
> observers is overwhelmingly likely to experience a sequence in proportion
> to its measure, not because the sequence itself is somehow weighted, but
> because there are simply more instances of the observer experiencing it.
>

There is no mechanism in unitary quantum mechanics that can give the
structure that you envisage.

This is not just an abstract claim—it follows directly from how measure
> works in probability. If you duplicate a computational process a million
> times and run it on different hardware, the subjective experience of that
> process does not exist in just one instance. Similarly, in MWI, if
> decoherence results in more observer instances in a high-measure region,
> then most self-locating observers will find themselves in those regions.
>

That does not work in unitary quantum mechanics.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-23 Thread John Clark

On Sat, Feb 22, 2025 at 7:00 PM Brent Meeker  wrote:

*>> You're just repeating the definition of the Born Rule, and everyone
>> agrees it works, but some of us would like to know WHY it works and WHY
>> it's even necessary given the fact that Schrodinger's equation is
>> deterministic *
>
>
> *> Well if you don't think it's "necessary"*
>

*Don't be ridiculous! I said the Born Rule was necessary.  What I asked is
WHY is it necessary?  *

*> science can only answer "why" questions if there is some more
> fundamental theory on which to base the answer. *
>

*And that theory was introduced by Hugh Everett in 1957 and improved by
Sean Carroll and David Deutsch and many many others over the last 68 years.
*

 > *just taking Schroedinger's equation as the basis is not sufficient.  So
> it clashes with the MWI mantra of "Just the Schroedinger equation*

*Everybody agrees that Schrodinger's equation works, and everybody agrees
it says something about what is going on at the deepest level of reality,
but some believe it can't be the entire story and there must be something
more that was happening. Many Worlds asks us to imagine what would be the
result if there was NOT something more going on and it was
just Schrodinger's equation.*

*Would an observer have enough information to make a prediction with an
arbitrary level of precision?*

*  No, and the fundamental reason why is that the observer himself must
also obey Schrodinger's equation, not just the thing he is trying to
predict. So there is no alternative but to resort to probability. *

*Is there a way to get a real number out of the complex 4-D wave that the
equation produces such that it's always between 0 and 1 and the
probabilities always add up to exactly 1? *

*Yes, take the absolute value of the wave function and then square it.*

*Mathematically is there another way to produce a set of numbers from
Schrodinger's wave that have the properties that a probability must have?
No, not if the complex wave is 3-D or higher.*

*What should a rational observer do if he wants to make bets about the
future? *

*Follow the Born Rule. *

*   John K ClarkSee what's on my new list at  Extropolis
*
dx5

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Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

My position is that the universe only exists through a conscious observer.
Conscious observers are more frequent in computations that generate a
stable environment rather than in isolated, short-lived computations that
just happen to produce a coherent perception. Without a conscious observer,
there is nothing—reality is an emergent property of observation.

I don’t claim to have a fully developed approach, otherwise, I would have
published it. But I think something along the lines of the UDA, combined
with constraints like the speed prior or compression-based measures, is
likely the right direction. The structure of reality might not be about
quantum mechanics alone but about how computational processes sustain
conscious experiences within it.

Quentin

Le dim. 23 févr. 2025, 04:34, Brent Meeker  a écrit :

>
>
> On 2/22/2025 4:49 PM, Quentin Anciaux wrote:
>
>
>
> Le dim. 23 févr. 2025, 01:39, Brent Meeker  a
> écrit :
>
>>
>>
>> On 2/22/2025 3:09 PM, Quentin Anciaux wrote:
>>
>> Bruce,
>>
>> Your argument assumes that because the Born rule is not yet fully derived
>> from unitary evolution, MWI must be incorrect.
>>
>> No, but it's only correct if you add the Born rule to it.  But that sort
>> of makes MWI, "Just the Schroedinger equation" wrong.  If it can't explain
>> the Born rule then postulating that every result happens just introduces an
>> extra complication.  With the Born rule we can just say one result obtains,
>> as predicted by the Born probability.
>>
>> Brent
>>
>
> Brent,
>
> Saying MWI is "only correct if you add the Born rule" is just another way
> of saying that quantum mechanics, in any interpretation, must account for
> why we observe Born-rule probabilities. That is not unique to MWI—every
> interpretation either assumes or derives it.
>
> That's what I said.  But you seem to think that the addition of the Born
> rule is unnecessary.  You think it can be derived.
>
>
> If you take the Born rule as a fundamental postulate, then yes, you can
> just say "one result obtains" without further justification. But that’s an
> assumption, not an explanation.
>
> And what would the explanation be.  What is the derivation of the Born
> rule without assuming it or something equivalent?
>
> The challenge is understanding why quantum probabilities follow this
> specific rule rather than any other distribution.
>
> I don't know why *understanding* it is a challenge.  It's empirically
> verified.  People understood that the sky is blue long before the atomic
> theory of matter.
>
> MWI does not introduce an extra complication—it raises the question of
> whether the Born rule follows from unitary evolution rather than being an
> additional postulate.
>
> And the answer is "No."
>
>
> If the Born rule cannot be derived from unitary evolution, that would be a
> major issue for MWI.
>
> Exactly so.  I makes MWI otiose.
>
> But that is not the same as saying it has been proven impossible. Simply
> assuming one result obtains because the Born rule says so does not address
> the deeper question of why it holds in the first place.
>
> It's impossible because as Bruce has pointed out MWI has no mechanism for
> producing uneven probabilities between two possibilities.
>
>
> That said, I personally think the real answer to these questions will not
> be found in MWI or any specific quantum interpretation, but in a
> computational theory of consciousness.
>
> Then you're welcome to publish such an answer.  But remember that the
> probabilities of quantum experiments are recorded in instruments that are
> far to simple to be conscious.
>
> Brent
>
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Re: Why even physicists still don’t understand quantum theory 100 years on

Le dim. 23 févr. 2025, 06:15, Brent Meeker  a écrit :

>
>
> On 2/12/2025 11:01 PM, Bruce Kellett wrote:
>
> On Thu, Feb 13, 2025 at 5:57 PM Quentin Anciaux 
> wrote:
>
>> Bruce,
>>
>> You argue that MWI predicts a uniform distribution of outcomes because
>> all sequences exist and each branch contains exactly one observer. Since
>> experiments follow the Born rule instead, you claim MWI is falsified. But
>> this assumes that measure has no effect—something you have not proven.
>>
>> The fact that 2^N sequences exist does not mean they all contribute
>> equally to an observer’s experience. That’s the core issue. If measure
>> determines how many copies of an observer exist in different branches, then
>> high-measure branches dominate experience. This would naturally lead to
>> Born-rule frequencies, without contradicting experiment.
>>
> Are you postulating more that 2^N sequences so the there can be more than
> one sequence of a given proportion of 1's and 0's with one observer each or
> are you postulating more than one observer in a given sequence?  The former
> corresponds to branch counting which JKC pointed out doesn't work because
> it would imply retroactive changes in amplitudes based on future
> measurement decisions.
>
>
>> Simply stating that each branch contains "one observer"
>>
> If a branch contains more that one observer they must still just observe
> the same sequence.  So they can't add to the weight of that sequence.
>

Brent,

You’re treating "branches" as isolated, discrete units, but if the
wavefunction remains a continuous superposition, then what we call "a
branch" is just an approximation—a macroscopic coarse-graining of many
micro-branches. Decoherence prevents interference between them, but it does
not imply a strict one-to-one mapping between observer instances and
branches.

If more observer instances exist in a high-amplitude region of the
wavefunction, then an observer randomly drawn from the total set of
observers is overwhelmingly likely to experience a sequence in proportion
to its measure, not because the sequence itself is somehow weighted, but
because there are simply more instances of the observer experiencing it.

This is not just an abstract claim—it follows directly from how measure
works in probability. If you duplicate a computational process a million
times and run it on different hardware, the subjective experience of that
process does not exist in just one instance. Similarly, in MWI, if
decoherence results in more observer instances in a high-measure region,
then most self-locating observers will find themselves in those regions.

So the issue isn’t that observers "add to the weight of a sequence"—the
weight already exists in the wavefunction amplitudes. The observer simply
finds themselves in a sequence that corresponds to their proportion in the
overall measure.

Quentin

> and that measure is irrelevant does not prove MWI is falsified—it assumes
>> your conclusion. If you want to show MWI is incompatible with experiment,
>> you need more than just claiming that measure plays no role; you need to
>> justify why quantum experiments consistently match despite your assertion
>> that all sequences should be equally likely.
>>
>
> The fact is that you get the same 2^N binary sequences from the binary
> state |psi> = a|0> + b|1> whatever the values of a and b. My case is proven.
>
> Bruce
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Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/12/2025 11:01 PM, Bruce Kellett wrote:
On Thu, Feb 13, 2025 at 5:57 PM Quentin Anciaux
wrote:

Bruce,

You argue that MWI predicts a uniform distribution of outcomes
because all sequences exist and each branch contains exactly one
observer. Since experiments follow the Born rule instead, you
claim MWI is falsified. But this assumes that measure has no
effect—something you have not proven.

The fact that 2^N sequences exist does not mean they all
contribute equally to an observer’s experience. That’s the core
issue. If measure determines how many copies of an observer exist
in different branches, then high-measure branches dominate
experience. This would naturally lead to Born-rule frequencies,
without contradicting experiment.

Are you postulating more that 2^N sequences so the there can be more
than one sequence of a given proportion of 1's and 0's with one observer
each or are you postulating more than one observer in a given sequence?
The former corresponds to branch counting which JKC pointed out doesn't
work because it would imply retroactive changes in amplitudes based on
future measurement decisions.

Simply stating that each branch contains "one observer"

If a branch contains more that one observer they must still just observe
the same sequence. So they can't add to the weight of that sequence.

and that measure is irrelevant does not prove MWI is falsified—it
assumes your conclusion. If you want to show MWI is incompatible
with experiment, you need more than just claiming that measure
plays no role; you need to justify why quantum experiments
consistently match despite your assertion that all sequences
should be equally likely.

The fact is that you get the same 2^N binary sequences from the binary
state |psi> = a|0> + b|1> whatever the values of a and b. My case is
proven.

Bruce
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Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/22/2025 4:49 PM, Quentin Anciaux wrote:

Le dim. 23 févr. 2025, 01:39, Brent Meeker a
écrit :

On 2/22/2025 3:09 PM, Quentin Anciaux wrote:

Bruce,

Your argument assumes that because the Born rule is not yet fully
derived from unitary evolution, MWI must be incorrect.

No, but it's only correct if you add the Born rule to it. But
that sort of makes MWI, "Just the Schroedinger equation" wrong.
If it can't explain the Born rule then postulating that every
result happens just introduces an extra complication. With the
Born rule we can just say one result obtains, as predicted by the
Born probability.

Brent

Brent,

Saying MWI is "only correct if you add the Born rule" is just another
way of saying that quantum mechanics, in any interpretation, must
account for why we observe Born-rule probabilities. That is not unique
to MWI—every interpretation either assumes or derives it.
That's what I said. But you seem to think that the addition of the Born
rule is unnecessary. You think it can be derived.

If you take the Born rule as a fundamental postulate, then yes, you
can just say "one result obtains" without further justification. But
that’s an assumption, not an explanation.
And what would the explanation be. What is the derivation of the Born
rule without assuming it or something equivalent?

The challenge is understanding why quantum probabilities follow this
specific rule rather than any other distribution.
I don't know why /understanding/ it is a challenge. It's empirically
verified. People understood that the sky is blue long before the atomic
theory of matter.

MWI does not introduce an extra complication—it raises the question of
whether the Born rule follows from unitary evolution rather than being
an additional postulate.

And the answer is "No."

If the Born rule cannot be derived from unitary evolution, that would
be a major issue for MWI.

Exactly so. I makes MWI otiose.

But that is not the same as saying it has been proven impossible.
Simply assuming one result obtains because the Born rule says so does
not address the deeper question of why it holds in the first place.
It's impossible because as Bruce has pointed out MWI has no mechanism
for producing uneven probabilities between two possibilities.

That said, I personally think the real answer to these questions will
not be found in MWI or any specific quantum interpretation, but in a
computational theory of consciousness.
Then you're welcome to publish such an answer. But remember that the
probabilities of quantum experiments are recorded in instruments that
are far to simple to be conscious.

Brent

Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-22 Thread Bruce Kellett

On Sun, Feb 23, 2025 at 11:44 AM Quentin Anciaux  wrote:

> Bruce,
>
> You argue that assuming the Born rule can emerge from unitary evolution is
> unjustified. But rejecting the possibility outright without proof is
> equally an assumption—one that dismisses ongoing efforts to derive it.
>

It is an assumption equivalent to your assumption that it is possible.
Given that many attempts to derive the Born rule from unitary evolution
have failed, then the evidence points to its general impossibility. It is a
major assumption to claim that, despite the evidence, this must be possible.

You claim that branch counting does not factor into your argument, yet your
> critique hinges on the idea that every binary sequence should appear with
> equal frequency.
>

That is a simple consequence of the construction. In each trial, the
observer splits into a copy that sees zero and a copy that sees one. These
two copies are equivalent.

After N such splits, we have 2^N binary sequences, all of which are
constructed from such 2-way splittings. So all are equivalent. Probability
does not come into it, because that concept has not been introduced at this
stage.

That assumption implicitly treats all branches as equiprobable, which is
> precisely what is in question.
>

The construction resolves this issue.

If measure determines observer distribution, then not all sequences
> contribute equally—just as in classical probability, where frequency
> matters more than raw enumeration.
>

Dismissing self-locating uncertainty as requiring a specific number of
> branches to match Born probabilities misrepresents the argument. The core
> idea is that high-measure branches contain exponentially more observer
> instances,
>

Where do the additional observers come from?. If they come from unitary
evolution, via decoherence or the equivalent, then they each come on a
separate branch, so counting them is just branch counting. If they come at
random, just by individuals  looking at the result on some branch, or from
random populations carried along with the observer as his branch splits,
then the number of such is not in your control. Those additional observers
are not the result of unitary evolution, and the number is certainly not
determined by any amplite of the initial wave function. So relying on
additional observers is either branch counting, or arrant nonsense.

making them overwhelmingly likely to be experienced. This is not an
> arbitrary assumption—it is a direct consequence of how amplitudes influence
> the evolution of the wavefunction.
>

It is pure fantasy on your part.

You state that no alternative approach can work, yet multiple avenues are
> actively being explored. Your argument does not refute MWI—it challenges
> one specific approach (branch counting) while ignoring others.
>

My argument has nothing to do with branch counting. You should get that
idea out of your head.

If you claim MWI is falsified, you need to address the broader question:
> why should amplitudes govern quantum behavior in every other context except
> observer frequencies?
>

Because the amplitudes play no role in determining the possible outcomes
from some measurement process. They may play other roles, but they are not
relevant here.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

Le dim. 23 févr. 2025, 01:39, Brent Meeker  a écrit :

>
>
> On 2/22/2025 3:09 PM, Quentin Anciaux wrote:
>
> Bruce,
>
> Your argument assumes that because the Born rule is not yet fully derived
> from unitary evolution, MWI must be incorrect.
>
> No, but it's only correct if you add the Born rule to it.  But that sort
> of makes MWI, "Just the Schroedinger equation" wrong.  If it can't explain
> the Born rule then postulating that every result happens just introduces an
> extra complication.  With the Born rule we can just say one result obtains,
> as predicted by the Born probability.
>
> Brent
>

Brent,

Saying MWI is "only correct if you add the Born rule" is just another way
of saying that quantum mechanics, in any interpretation, must account for
why we observe Born-rule probabilities. That is not unique to MWI—every
interpretation either assumes or derives it.

If you take the Born rule as a fundamental postulate, then yes, you can
just say "one result obtains" without further justification. But that’s an
assumption, not an explanation. The challenge is understanding why quantum
probabilities follow this specific rule rather than any other distribution.
MWI does not introduce an extra complication—it raises the question of
whether the Born rule follows from unitary evolution rather than being an
additional postulate.

If the Born rule cannot be derived from unitary evolution, that would be a
major issue for MWI. But that is not the same as saying it has been proven
impossible. Simply assuming one result obtains because the Born rule says
so does not address the deeper question of why it holds in the first place.

That said, I personally think the real answer to these questions will not
be found in MWI or any specific quantum interpretation, but in a
computational theory of consciousness. The key issue is not just how
probabilities emerge, but how subjective experience is structured within
the mathematical framework of physics. If consciousness is fundamentally
computational, then probability might arise from the self-sampling of
computational processes rather than purely from wavefunction amplitudes.

Quentin

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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

You argue that assuming the Born rule can emerge from unitary evolution is
unjustified. But rejecting the possibility outright without proof is
equally an assumption—one that dismisses ongoing efforts to derive it.

You claim that branch counting does not factor into your argument, yet your
critique hinges on the idea that every binary sequence should appear with
equal frequency. That assumption implicitly treats all branches as
equiprobable, which is precisely what is in question. If measure determines
observer distribution, then not all sequences contribute equally—just as in
classical probability, where frequency matters more than raw enumeration.

Dismissing self-locating uncertainty as requiring a specific number of
branches to match Born probabilities misrepresents the argument. The core
idea is that high-measure branches contain exponentially more observer
instances, making them overwhelmingly likely to be experienced. This is not
an arbitrary assumption—it is a direct consequence of how amplitudes
influence the evolution of the wavefunction.

You state that no alternative approach can work, yet multiple avenues are
actively being explored. Your argument does not refute MWI—it challenges
one specific approach (branch counting) while ignoring others. If you claim
MWI is falsified, you need to address the broader question: why should
amplitudes govern quantum behavior in every other context except observer
frequencies?

If your argument were definitive, it would be publishable. But simply
stating "it hasn’t been done" is not a proof that it cannot be done.

Quentin

Le dim. 23 févr. 2025, 00:31, Bruce Kellett  a
écrit :

> On Sun, Feb 23, 2025 at 10:09 AM Quentin Anciaux 
> wrote:
>
>> Bruce,
>>
>> Your argument assumes that because the Born rule is not yet fully derived
>> from unitary evolution, MWI must be incorrect. But that’s not a proof—it’s
>> just an assertion of incompleteness.
>>
>
> On the other hand, it is just an assumption that it can be made to work --
> an assumption without any evidential support.
>
> You claim to have refuted MWI, but what you have shown is that naive
>> branch counting does not recover the Born rule. That’s not news—Everettians
>> don’t rely on branch counting alone. The real question is whether measure,
>> derived from amplitudes, determines observer frequencies.
>>
>
> Clearly you have not made any effort to understand what I have been
> saying. Branch counting does not come into the argument. The only place
> where branch counting might be relevant is if you rely on self-locating
> uncertainty. Then you require the number of branches to reflect the Born
> probabilities. That does not work.
>
>
> You keep insisting that amplitudes play no role beyond the Born rule, but
>> this is circular—you are assuming the Born rule as a fundamental postulate
>> rather than allowing for the possibility that it emerges from the structure
>> of unitary evolution. If you claim that no such derivation is possible, you
>> need more than a rejection of branch counting—you need to demonstrate why
>> no alternative approach could work.
>>
>
> You clearly don't even understand what a circular argument is.
>
> If you believe MWI is falsified, publish your proof. Otherwise, saying "it
>> hasn’t been done yet" is not the same as showing it can’t be done.
>>
>
> Publication is not proof.
>
> Bruce
>
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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/22/2025 3:09 PM, Quentin Anciaux wrote:

Bruce,

Your argument assumes that because the Born rule is not yet fully 
derived from unitary evolution, MWI must be incorrect.
No, but it's only correct if you add the Born rule to it.  But that sort 
of makes MWI, "Just the Schroedinger equation" wrong.  If it can't 
explain the Born rule then postulating that every result happens just 
introduces an extra complication.  With the Born rule we can just say 
one result obtains, as predicted by the Born probability.


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/22/2025 1:38 PM, John Clark wrote:
On Sat, Feb 22, 2025 at 3:00 PM Brent Meeker
wrote:

>> On 2/21/2025 11:03 PM, Quentin Anciaux wrote:
If amplitude plays no role in observer distribution, then why
does the Born rule hold?

/> The squared amplitude determines the relative frequency of
results in repeated trials. /

*That doesn't answer Quentin's question. *
His question implied that the Born rule was realized by having different
numbers of observers in different branches. I answered that it's not
different numbers of observers but different proportions of results in
repeated trials. So it's just as much an answer as his, except it's
operational: we can count and record the result sequences...but the
number of observers is indeterminate.

*You're just repeating the definition of the Born Rule, and everyone
agrees it works, but some of us would like to know WHY it works and
WHY it's even necessary given the fact that Schrodinger's equation is
deterministic *
Well if you don't think it's "necessary" I invite you to try doing QM
without it. As I've pointed out several times, science can only answer
"why" questions if there is some more fundamental theory on which to
base the answer. Every scientist wants to know why. But just taking
Schroedinger's equation as the basis is not sufficient. So it clashes
with the MWI mantra of "Just the Schroedinger equation". Given that the
Schroedinger equation doesn't logically imply the Born rule, the next
simplest is just to add the Born rule as an axiom of the theory.

What is not valid is to just assert the Born rule must derive from the
Schoredinger equation somehow, without spelling out the derivation.

*but others, such as yourself, are content to just shut up and
calculate. To each their own.

Don't tell me what I'm content with.

Brent

*John K Clark See what's on my new list at Extropolis
*

csu

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Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/22/2025 2:00 PM, Quentin Anciaux wrote:

Le sam. 22 févr. 2025, 21:01, Brent Meeker a
écrit :

On 2/21/2025 11:19 PM, Quentin Anciaux wrote:

You're just restating that amplitudes only matter for
probabilities because of the Born rule, which is exactly the
point in question. You're assuming what you need to prove.

Proof is for printers, mathematicians, and whiskey. Science goes
by evidence.

Brent

We confirmed the Born rule empirically, yes. But the question is why
it holds in a purely unitary framework.
Yes, good question. But just saying it does is not help. If you have a
derivation, publish it. A lot of people have tried and each try has
been found wanting.

If science goes by evidence, then interpretations must account for
that evidence.
That's flat out nonsense. Interpretations, by definition, are just
stories that relate a theory to facts. They don't add to the theory.

Just stating that squared amplitudes determine frequencies doesn’t
explain why they should without assuming it outright.
True. But so far it is simpler than any of the other, logically
equivalent additions to the theory that have been proposed.

Brent

Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-22 Thread Bruce Kellett

On Sun, Feb 23, 2025 at 10:09 AM Quentin Anciaux  wrote:

> Bruce,
>
> Your argument assumes that because the Born rule is not yet fully derived
> from unitary evolution, MWI must be incorrect. But that’s not a proof—it’s
> just an assertion of incompleteness.
>

On the other hand, it is just an assumption that it can be made to work --
an assumption without any evidential support.

You claim to have refuted MWI, but what you have shown is that naive branch
> counting does not recover the Born rule. That’s not news—Everettians don’t
> rely on branch counting alone. The real question is whether measure,
> derived from amplitudes, determines observer frequencies.
>

Clearly you have not made any effort to understand what I have been saying.
Branch counting does not come into the argument. The only place where
branch counting might be relevant is if you rely on self-locating
uncertainty. Then you require the number of branches to reflect the Born
probabilities. That does not work.


You keep insisting that amplitudes play no role beyond the Born rule, but
> this is circular—you are assuming the Born rule as a fundamental postulate
> rather than allowing for the possibility that it emerges from the structure
> of unitary evolution. If you claim that no such derivation is possible, you
> need more than a rejection of branch counting—you need to demonstrate why
> no alternative approach could work.
>

You clearly don't even understand what a circular argument is.

If you believe MWI is falsified, publish your proof. Otherwise, saying "it
> hasn’t been done yet" is not the same as showing it can’t be done.
>

Publication is not proof.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

Le sam. 22 févr. 2025, 21:01, Brent Meeker  a écrit :

>
>
> On 2/21/2025 11:19 PM, Quentin Anciaux wrote:
>
> You're just restating that amplitudes only matter for probabilities
> because of the Born rule, which is exactly the point in question. You're
> assuming what you need to prove.
>
> Proof is for printers, mathematicians, and whiskey.  Science goes by
> evidence.
>
> Brent
>

We confirmed the Born rule empirically, yes. But the question is why it
holds in a purely unitary framework. If science goes by evidence, then
interpretations must account for that evidence. Just stating that squared
amplitudes determine frequencies doesn’t explain why they should without
assuming it outright.

Quentin

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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

Your argument assumes that because the Born rule is not yet fully derived
from unitary evolution, MWI must be incorrect. But that’s not a proof—it’s
just an assertion of incompleteness.

You claim to have refuted MWI, but what you have shown is that naive branch
counting does not recover the Born rule. That’s not news—Everettians don’t
rely on branch counting alone. The real question is whether measure,
derived from amplitudes, determines observer frequencies.

You keep insisting that amplitudes play no role beyond the Born rule, but
this is circular—you are assuming the Born rule as a fundamental postulate
rather than allowing for the possibility that it emerges from the structure
of unitary evolution. If you claim that no such derivation is possible, you
need more than a rejection of branch counting—you need to demonstrate why
no alternative approach could work.

If you believe MWI is falsified, publish your proof. Otherwise, saying "it
hasn’t been done yet" is not the same as showing it can’t be done.

Quentin

Le sam. 22 févr. 2025, 23:47, Bruce Kellett  a
écrit :

> On Sun, Feb 23, 2025 at 9:01 AM Quentin Anciaux 
> wrote:
>
>> Le sam. 22 févr. 2025, 21:01, Brent Meeker  a
>> écrit :
>>
>>> On 2/21/2025 11:19 PM, Quentin Anciaux wrote:
>>>
>>> You're just restating that amplitudes only matter for probabilities
>>> because of the Born rule, which is exactly the point in question. You're
>>> assuming what you need to prove.
>>>
>>> Proof is for printers, mathematicians, and whiskey.  Science goes by
>>> evidence.
>>>
>>> Brent
>>>
>>
>> We confirmed the Born rule empirically, yes. But the question is why it
>> holds in a purely unitary framework. If science goes by evidence, then
>> interpretations must account for that evidence. Just stating that squared
>> amplitudes determine frequencies doesn’t explain why they should without
>> assuming it outright.
>>
>
> That argument might have more weight if you could actually give a coherent
> account of the origin of probability and the Born rule in terms of unitary
> evolution.
>
> Bruce
>
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> .
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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-22 Thread Bruce Kellett

On Sun, Feb 23, 2025 at 9:01 AM Quentin Anciaux  wrote:

> Le sam. 22 févr. 2025, 21:01, Brent Meeker  a
> écrit :
>
>> On 2/21/2025 11:19 PM, Quentin Anciaux wrote:
>>
>> You're just restating that amplitudes only matter for probabilities
>> because of the Born rule, which is exactly the point in question. You're
>> assuming what you need to prove.
>>
>> Proof is for printers, mathematicians, and whiskey.  Science goes by
>> evidence.
>>
>> Brent
>>
>
> We confirmed the Born rule empirically, yes. But the question is why it
> holds in a purely unitary framework. If science goes by evidence, then
> interpretations must account for that evidence. Just stating that squared
> amplitudes determine frequencies doesn’t explain why they should without
> assuming it outright.
>

That argument might have more weight if you could actually give a coherent
account of the origin of probability and the Born rule in terms of unitary
evolution.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-22 Thread John Clark

On Sat, Feb 22, 2025 at 3:00 PM Brent Meeker  wrote:

>> On 2/21/2025 11:03 PM, Quentin Anciaux wrote:
>> If amplitude plays no role in observer distribution, then why does the
>> Born rule hold?
>
>

* > The squared amplitude determines the relative frequency of results in
> repeated trials. *
>

*That doesn't answer Quentin's question. You're just repeating the
definition of the Born Rule, and everyone agrees it works, but some of us
would like to know WHY it works and WHY it's even necessary given the fact
that Schrodinger's equation is deterministic but others, such as yourself,
are content to just shut up and calculate. To each their own.  *

*John K ClarkSee what's on my new list at  Extropolis
*

csu

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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/21/2025 11:19 PM, Quentin Anciaux wrote:
You're just restating that amplitudes only matter for probabilities 
because of the Born rule, which is exactly the point in question. 
You're assuming what you need to prove.
Proof is for printers, mathematicians, and whiskey.  Science goes by 
evidence.


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/21/2025 11:03 PM, Quentin Anciaux wrote:
If amplitude plays no role in observer distribution, then why does the 
Born rule hold?


The squared amplitude determines the relative frequency of results in 
repeated trials.


How do you think we confirmed the Born rule.

Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-22 Thread John Clark

On Fri, Feb 21, 2025 at 6:10 PM Brent Meeker  wrote:

*>> One of you sees a live cat in the box and another of you sees a dead
>> cat in the box and each observation causes the world and everybody in it to
>> split; however unless those other people have interacted with you they will
>> not have changed. And two conscious brains that are identical is
>> indistinguishable from one both subjectively and objectively. And if
>> there's no subjective difference and there's no objective difference then
>> there is just no difference.*
>
>

*>Those "other people" need only have interacted with a particle that has
> interacted with a particle that has interacted with the Geiger counter that
> triggered the gas. *
>

*Yes, but most particles have not reacted with a geiger counter, and even
if one had in most cases you personally would not be conscious of it having
done so. *

*> You're not supposing that only conscious differences implement splits,
> are you?*

*No. Any change  to your body, no matter how small, will cause the universe
to split. However you will not be consciously aware of all, or even most,
of those changes. In other words, a change in the quantum state of one
electron in your big toe will not change the way you process information at
the instant the universe splits; although, because of classical chaos, it
might cause a change in your information processing, and therefore your
consciousness, sometime in the future.*

*John K ClarkSee what's on my new list at  Extropolis
*

ty

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Re: Why even physicists still don’t understand quantum theory 100 years on

Le sam. 22 févr. 2025, 08:09, Bruce Kellett  a
écrit :

> On Sat, Feb 22, 2025 at 6:03 PM Quentin Anciaux 
> wrote:
>
>> Brent,
>>
>> You say the Born rule is justified empirically, which is true. But
>> empirical justification is not the same as theoretical derivation. If we
>> only appeal to empirical evidence, then we are just restating that the rule
>> works, not explaining why it follows from unitary evolution.
>>
>> The problem isn’t whether the Born rule is correct—it clearly is—but
>> whether its connection to amplitude can be derived within MWI rather than
>> imposed. Saying "probabilities are just what happens" is not an
>> explanation, it’s an assertion.
>>
>> You keep insisting that decoherence doesn’t justify why amplitudes should
>> determine observer frequency. But if amplitudes dictate the behavior of
>> quantum systems in all other cases, why would they suddenly stop mattering
>> when it comes to what observers experience? You haven’t answered
>> that—you’ve just stated that amplitudes don’t determine frequency without
>> justification.
>>
>> As for the "bush of worlds," decoherence doesn’t create separate
>> worlds—it describes why interference becomes negligible, leading to
>> effectively independent branches. The number of observer instances per
>> branch is what’s at stake. If amplitude plays no role in observer
>> distribution, then why does the Born rule hold?
>>
>> If you believe MWI cannot account for the Born rule, then you need a
>> reason why amplitudes should stop affecting probabilities at the moment of
>> measurement, despite governing quantum evolution everywhere else.
>> Otherwise, you’re just stating the rule rather than explaining it.
>>
>
> Maybe that is one of your fundamental mistakes: the idea that amplitudes
> affect quantum outcomes in all instances. That fact is that their only
> significance is in determining probabilities via the Born rule. They play
> no other role. This is easily proved by the examples I have given.
>
> Bruce
>

Bruce,

You're just restating that amplitudes only matter for probabilities because
of the Born rule, which is exactly the point in question. You're assuming
what you need to prove.

If amplitudes have no role beyond determining probabilities, then where do
those probabilities come from? Why should an observer expect them to follow
the squared amplitude rather than some other function? Saying "that's just
how the Born rule works" is circular reasoning.

In every other quantum phenomenon, amplitudes influence measurable
effects—interference patterns, energy levels, and system evolution under
the Schrödinger equation. Why would measurement be the only exception,
where amplitudes suddenly become irrelevant except as a post hoc
probability assignment?

Your examples don’t "prove" amplitudes play no role—they assume it by
treating all sequences as equal. But that’s precisely the issue: if measure
matters, then sequences are not equally likely from an observer’s
perspective, and the Born rule follows naturally.

Should I repeat that I’m not an advocate of MWI? I believe the real
solution, if there is one, lies in a computational theory of mind. But
you’re too focused on being an ‘opponent’ to engage with the ideas
properly. That distraction keeps you from reading and thinking critically.
And again, if you’re so confident, publish your refutation and claim the
recognition you seek.

Quentin

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Re: Why even physicists still don’t understand quantum theory 100 years on

On Sat, Feb 22, 2025 at 6:03 PM Quentin Anciaux  wrote:

> Brent,
>
> You say the Born rule is justified empirically, which is true. But
> empirical justification is not the same as theoretical derivation. If we
> only appeal to empirical evidence, then we are just restating that the rule
> works, not explaining why it follows from unitary evolution.
>
> The problem isn’t whether the Born rule is correct—it clearly is—but
> whether its connection to amplitude can be derived within MWI rather than
> imposed. Saying "probabilities are just what happens" is not an
> explanation, it’s an assertion.
>
> You keep insisting that decoherence doesn’t justify why amplitudes should
> determine observer frequency. But if amplitudes dictate the behavior of
> quantum systems in all other cases, why would they suddenly stop mattering
> when it comes to what observers experience? You haven’t answered
> that—you’ve just stated that amplitudes don’t determine frequency without
> justification.
>
> As for the "bush of worlds," decoherence doesn’t create separate worlds—it
> describes why interference becomes negligible, leading to effectively
> independent branches. The number of observer instances per branch is what’s
> at stake. If amplitude plays no role in observer distribution, then why
> does the Born rule hold?
>
> If you believe MWI cannot account for the Born rule, then you need a
> reason why amplitudes should stop affecting probabilities at the moment of
> measurement, despite governing quantum evolution everywhere else.
> Otherwise, you’re just stating the rule rather than explaining it.
>

Maybe that is one of your fundamental mistakes: the idea that amplitudes
affect quantum outcomes in all instances. That fact is that their only
significance is in determining probabilities via the Born rule. They play
no other role. This is easily proved by the examples I have given.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

You say the Born rule is justified empirically, which is true. But
empirical justification is not the same as theoretical derivation. If we
only appeal to empirical evidence, then we are just restating that the rule
works, not explaining why it follows from unitary evolution.

The problem isn’t whether the Born rule is correct—it clearly is—but
whether its connection to amplitude can be derived within MWI rather than
imposed. Saying "probabilities are just what happens" is not an
explanation, it’s an assertion.

You keep insisting that decoherence doesn’t justify why amplitudes should
determine observer frequency. But if amplitudes dictate the behavior of
quantum systems in all other cases, why would they suddenly stop mattering
when it comes to what observers experience? You haven’t answered
that—you’ve just stated that amplitudes don’t determine frequency without
justification.

As for the "bush of worlds," decoherence doesn’t create separate worlds—it
describes why interference becomes negligible, leading to effectively
independent branches. The number of observer instances per branch is what’s
at stake. If amplitude plays no role in observer distribution, then why
does the Born rule hold?

If you believe MWI cannot account for the Born rule, then you need a reason
why amplitudes should stop affecting probabilities at the moment of
measurement, despite governing quantum evolution everywhere else.
Otherwise, you’re just stating the rule rather than explaining it.

Quentin

Le sam. 22 févr. 2025, 02:26, Brent Meeker  a écrit :

>
>
> On 2/21/2025 1:41 PM, Quentin Anciaux wrote:
>
> Brent,
>
> The Born rule is not something that "should" be obeyed—it is obeyed in
> experiments. The question is why. Saying "some things happen and others
> don’t" doesn’t answer that.
>
> That's my answer to what probabilities mean.  And the Born rule says the
> squared amplitudes of Schroedinger's equation should be interpreted as
> probabilities.
>
> If amplitudes determine the behavior of quantum systems in every other
> context, why would they suddenly become meaningless when it comes to
> observer experiences? That’s what you need to justify.
>
> It's justified empirically.  You're the one claiming in follows from the
> Schroedinger equation.  Justify that.
>
>
> You claim that talking about observers is "obfuscation," but probability
> itself is about expectations—what an observer should expect to see given
> the structure of the theory. If multiple observers look at the same SG
> detector, yes, they all see UP. But why was that outcome observed with
> probability a² rather than any other distribution?
>
> Because the Born rule. But according you it's because somehow decoherence
> produces a bush or identical worlds for each outcome.
>
> Ignoring that question doesn’t make it go away.
>
> Ignoring that having ten people in room looking at the result doesn't
> increase it's probability doesn't help.  So where is your explanation of
> how the bush of worlds gets produced?
>
>
> The challenge for any interpretation—whether MWI, collapse, or anything
> else—is to explain why experiments follow the Born rule. Dismissing the
> problem as circular without engaging with why amplitudes might determine
> observer frequencies is avoiding the issue, not resolving it.
>
> We've know for over a century that the amplitudes determine the
> frequencies, that was Born's insight.  But that's just stating the Born
> rule.  Science can only answer "Why?" questions in terms of deeper theory.
> So far none has been forthcoming.
>
> Brent
>
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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

You assume that branch counting alone determines probabilities, but that
assumption is precisely what’s in question. If observer instances are
proportional to amplitude, then probability follows naturally without
needing to impose it.

Decoherence creates effectively independent branches, but nothing in
quantum mechanics states that all branches contribute equally. If you
assume they do, you are assuming what you need to prove—namely, that
amplitudes play no role in observer distribution.

A simple analogy: if you run the same conscious program on multiple
machines, each instance experiences the same thing. If 9 instances see "1"
and 1 instance sees "0," then the subjective probability of seeing "1" is
90%, despite all outcomes existing. That is not branch counting—it’s a
direct consequence of duplication asymmetry.

You claim that "the evidence is against me," but provide no mechanism
explaining why we should ignore amplitude. If you believe MWI cannot
recover Born’s rule, then you need more than branch counting—you need to
explain why experimental probabilities match a rule that, under your logic,
should not emerge at all.

Quentin

Le ven. 21 févr. 2025, 23:46, Bruce Kellett  a
écrit :

> On Sat, Feb 22, 2025 at 9:19 AM Quentin Anciaux 
> wrote:
>
>> Brent,
>>
>> Consider a simple computational analogy: if consciousness is a program,
>> running multiple instances of it doesn’t create different "people"—it just
>> creates more instances of the same subjective experience.
>>
>> Now, imagine we take a program that simulates an observer. We run it 9
>> times on computers that display "1" on the screen and once on a computer
>> that displays "0". Each instance of the program experiences seeing either
>> "1" or "0", but the overwhelming majority experience "1".
>>
>> This mirrors how observer instances distribute in MWI: more instances
>> exist in high-amplitude branches. The program has no way to distinguish
>> whether it's in a "common" or "rare" instance, but if you were to randomly
>> select an instance, it would most likely be one that sees "1".
>>
>> This is the key distinction: probability in MWI doesn’t come from
>> counting branches; it comes from the relative number of observer instances
>> in each. The Born rule follows naturally if amplitude determines observer
>> frequency—just as in the example, where the majority of observer instances
>> see "1" despite both outcomes occurring.
>>
>
> Prove that the amplitude determines observer frequency - the evidence is
> all against you. It is clear that the Schrodinger equation does not act on
> amplitudes.
>
> Decoherence does increase the number of copies of an observer on a
> particular branch (or, better, related branches). But that just
> demonstrates that your "preponderance of observers" is no more than simp[le
> branch counting.
>
> Bruce
>
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> 
> .
>

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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/21/2025 2:19 PM, Quentin Anciaux wrote:

Brent,

Consider a simple computational analogy: if consciousness is a 
program, running multiple instances of it doesn’t create different 
"people"—it just creates more instances of the same subjective experience.

Not if has different input: eyes in different places for example.


Now, imagine we take a program that simulates an observer. We run it 9 
times on computers that display "1" on the screen and once on a 
computer that displays "0". Each instance of the program experiences 
seeing either "1" or "0", but the overwhelming majority experience "1".


This mirrors how observer instances distribute in MWI:
That's the question.  That's what needs to be explained.  But you always 
just assert  it a some point and then say, "See I've explained it.  And 
it must be explained."


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/21/2025 2:10 PM, Quentin Anciaux wrote:

Brent,

I’m not just repeating that the Born rule works—I’m pointing out that
any valid interpretation must explain why it works.
That's nonsense. I don't think you know who science works. What's the
explanation for gravity going as 1/r^2? What's a valid interpretation
of gravity?

You keep arguing as if I’m assuming it, but the argument is that
measure provides a natural way to account for it without assuming it
outright.
Natural or not, we know empirically the Born rule works. You just keep
making up stories that end in "and that's why the Born rule works." And
since the Born rule does work that makes you story true.

The lottery analogy illustrates this: more copies of an observer in a
high-measure branch means an observer is overwhelmingly likely to
experience that outcome. This is not about assuming the Born rule—it’s
about showing how a distribution naturally arises from the structure
of the wavefunction.
How does "naturally arises" work. If you going to have an explanation
that actually explains, it can't depend on vague phrases like "naturally
arises". That's no better than "it works".

You seem to interpret "more observers" as meaning entirely separate
people in the same world. That’s not what’s being said. If the
wavefunction remains a continuous superposition, then what we call "a
branch" isn’t a single, discrete entity—it’s a coarse partition in an
underlying structure. More observers in a branch means more instances
of the same observer, not more independent individuals.

If you think this fails to explain the Born rule, then the burden is
on you to show why. Just stating that the Schrödinger equation doesn’t
explicitly derive it ignores the fact that all interpretations rely on
additional reasoning to connect math to experience. Dismissing this as
"assuming what needs to be proven" without engaging with how measure
distributes observer instances doesn’t resolve anything.
Maybe you should read those papers purporting to derive the Born rule.
And then read the critiques that show how they are circular or slip in
extra assumptions.

Brent

Re: Why even physicists still don’t understand quantum theory 100 years on

On 2/21/2025 1:41 PM, Quentin Anciaux wrote:

Brent,

The Born rule is not something that "should" be obeyed—it is obeyed in
experiments. The question is why. Saying "some things happen and
others don’t" doesn’t answer that.
That's my answer to what probabilities mean. And the Born rule says the
squared amplitudes of Schroedinger's equation should be interpreted as
probabilities.

If amplitudes determine the behavior of quantum systems in every other
context, why would they suddenly become meaningless when it comes to
observer experiences? That’s what you need to justify.
It's justified empirically. You're the one claiming in follows from the
Schroedinger equation. Justify that.

You claim that talking about observers is "obfuscation," but
probability itself is about expectations—what an observer should
expect to see given the structure of the theory. If multiple observers
look at the same SG detector, yes, they all see UP. But why was that
outcome observed with probability a² rather than any other distribution?
Because the Born rule. But according you it's because somehow
decoherence produces a bush or identical worlds for each outcome.

Ignoring that question doesn’t make it go away.
Ignoring that having ten people in room looking at the result doesn't
increase it's probability doesn't help. So where is your explanation of
how the bush of worlds gets produced?

The challenge for any interpretation—whether MWI, collapse, or
anything else—is to explain why experiments follow the Born rule.
Dismissing the problem as circular without engaging with why
amplitudes might determine observer frequencies is avoiding the issue,
not resolving it.
We've know for over a century that the amplitudes determine the
frequencies, that was Born's insight. But that's just stating the Born
rule. Science can only answer "Why?" questions in terms of deeper
theory. So far none has been forthcoming.

Brent

Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-21 Thread Russell Standish

On Fri, Feb 21, 2025 at 07:22:38PM +1100, Bruce Kellett wrote:
> On Fri, Feb 21, 2025 at 5:16 PM Brent Meeker  wrote:
> 
> Brent,
> 
> This is beginning to sound like an argument we had with someone on another
> list. His final position in that case was that, although he could not give
> comprehensive arguments for his contentions, it had to be that way if his
> theory was correct.
> 
> This is precisely where Quentin is currently. He keeps making extrordinary
> claims without any shred of justification -- because if these claimds are not
> so then his theory is in trouble.
> 
> The simplest conclusion is that his theory is not correct.
> 
> Bruce

Bruce - the ony way you can do branch counting to get measure is if
the branches obey a physically symmetry. Then you can apply the
indifference principle - just as you say the probability of a die
outcome is 1/6th, you can say the probability of up or down is
1/2. But by construction, your "counter example" does not have
symmetric branches, therefore branch counting does not apply. All we
can say is that there will be some probability of each outcome. Just
like slicing a cake, you can slice the Multiverse in many different
ways, with different effects on the measure.

Quentin is not claiming to be able to generate the Born rule from all
of this, just that it is an open problem. Some say the Gleason theorem
is sufficient for this. My own derivation sort of goes the other
way. Starting with a probability measure attached to each branch, you
can construct an inner product space (and prove it is a Hilbert space)
that gives you the Born rule. Is this the only way of constructing an
inner product space? The Gleason theorem suggests it is.

What would be nice is to have all of that arise naturally from
information processing considerations. I don't know if that is
possible. It might be we need to augment our theory of computation
with something like quantum computation, for example.

-- 

Dr Russell StandishPhone 0425 253119 (mobile)
Principal, High Performance Coders hpco...@hpcoders.com.au
  http://www.hpcoders.com.au

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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/21/2025 4:04 AM, John Clark wrote:
On Fri, Feb 21, 2025 at 12:39 AM Bruce Kellett  
wrote:


/>  a 'branch' encompasses the whole world, so if you want more
than one person on each branch, you have the entire population of
the world on each branch./


*Yes.*

/> Unfortunately, the same population can be found on every branch, /

*
*
*Yes, but I don't see why you say that is "unfortunate". *


/>so that does not give you the necessary partitioning according
to branch weight./


*One of you sees a live cat in the box and another of you sees a dead 
cat in the box and each observation causes the world and everybody in 
it to split; however unless those other people have interacted with 
you they will not have changed. And two conscious brains that are 
identical is indistinguishable from one both subjectively and 
objectively. And if there's no subjective difference and there's no 
objective difference then there is just no difference.

*
Those "other people" need only have interacted with a particle that has 
interacted with a particle that has interacted with the Geiger counter 
that triggered the gas.  That's why the usual theory is that the split 
of the two worlds propagates roughly at the speed of light (since those 
particles could be photons). You're not supposing that only conscious 
differences implement splits, are you?


Brent


*John K Clark    See what's on my new list at Extropolis 
*

4ej




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Re: Why even physicists still don’t understand quantum theory 100 years on

On Sat, Feb 22, 2025 at 9:19 AM Quentin Anciaux  wrote:

> Brent,
>
> Consider a simple computational analogy: if consciousness is a program,
> running multiple instances of it doesn’t create different "people"—it just
> creates more instances of the same subjective experience.
>
> Now, imagine we take a program that simulates an observer. We run it 9
> times on computers that display "1" on the screen and once on a computer
> that displays "0". Each instance of the program experiences seeing either
> "1" or "0", but the overwhelming majority experience "1".
>
> This mirrors how observer instances distribute in MWI: more instances
> exist in high-amplitude branches. The program has no way to distinguish
> whether it's in a "common" or "rare" instance, but if you were to randomly
> select an instance, it would most likely be one that sees "1".
>
> This is the key distinction: probability in MWI doesn’t come from counting
> branches; it comes from the relative number of observer instances in each.
> The Born rule follows naturally if amplitude determines observer
> frequency—just as in the example, where the majority of observer instances
> see "1" despite both outcomes occurring.
>

Prove that the amplitude determines observer frequency - the evidence is
all against you. It is clear that the Schrodinger equation does not act on
amplitudes.

Decoherence does increase the number of copies of an observer on a
particular branch (or, better, related branches). But that just
demonstrates that your "preponderance of observers" is no more than simp[le
branch counting.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

Consider a simple computational analogy: if consciousness is a program,
running multiple instances of it doesn’t create different "people"—it just
creates more instances of the same subjective experience.

Now, imagine we take a program that simulates an observer. We run it 9
times on computers that display "1" on the screen and once on a computer
that displays "0". Each instance of the program experiences seeing either
"1" or "0", but the overwhelming majority experience "1".

This mirrors how observer instances distribute in MWI: more instances exist
in high-amplitude branches. The program has no way to distinguish whether
it's in a "common" or "rare" instance, but if you were to randomly select
an instance, it would most likely be one that sees "1".

This is the key distinction: probability in MWI doesn’t come from counting
branches; it comes from the relative number of observer instances in each.
The Born rule follows naturally if amplitude determines observer
frequency—just as in the example, where the majority of observer instances
see "1" despite both outcomes occurring.

Quentin

Le ven. 21 févr. 2025, 23:10, Quentin Anciaux  a écrit :

> Brent,
>
> I’m not just repeating that the Born rule works—I’m pointing out that any
> valid interpretation must explain why it works. You keep arguing as if I’m
> assuming it, but the argument is that measure provides a natural way to
> account for it without assuming it outright.
>
> The lottery analogy illustrates this: more copies of an observer in a
> high-measure branch means an observer is overwhelmingly likely to
> experience that outcome. This is not about assuming the Born rule—it’s
> about showing how a distribution naturally arises from the structure of the
> wavefunction.
>
> You seem to interpret "more observers" as meaning entirely separate people
> in the same world. That’s not what’s being said. If the wavefunction
> remains a continuous superposition, then what we call "a branch" isn’t a
> single, discrete entity—it’s a coarse partition in an underlying structure.
> More observers in a branch means more instances of the same observer, not
> more independent individuals.
>
> If you think this fails to explain the Born rule, then the burden is on
> you to show why. Just stating that the Schrödinger equation doesn’t
> explicitly derive it ignores the fact that all interpretations rely on
> additional reasoning to connect math to experience. Dismissing this as
> "assuming what needs to be proven" without engaging with how measure
> distributes observer instances doesn’t resolve anything.
>
> Quentin
>
> Le ven. 21 févr. 2025, 22:59, Brent Meeker  a
> écrit :
>
>>
>>
>> On 2/20/2025 11:30 PM, Quentin Anciaux wrote:
>>
>> Brent,
>>
>> The Schroedinger equation governs the evolution of the wavefunction, but
>> decoherence determines the effective structure of branches.
>>
>> A branch is defined the result of the measurement.  If the electron spin
>> is UP, then that defined the UP branch.  Decoherence presumably spreads
>> from the SG detector and makes a world around UP that's orthogonal to the
>> world around DWN.  "Effective structure" beyond this is just your invention.
>>
>> When I say a branch isn’t a single discrete unit, I mean that what we
>> call a “branch” is an approximation—a macroscopic, emergent structure from
>> the underlying quantum evolution.
>>
>> Why isn't it single in the sense that it is the branch that originated
>> from a single measurement value.  "emergent structure from the underlying
>> quantum evolution" is just obfuscation.
>>
>> The wavefunction never truly “splits” into countable, independent worlds;
>> rather, it evolves into a superposition of decohered, non-interfering
>> components, which we approximate as separate branches.
>>
>> If they are non-interfering they are in a superposition.  They're
>> orthogonal.
>>
>>
>> The fact that different results are orthogonal doesn’t mean each result
>> corresponds to exactly one observer copy.
>>
>> The UP world originated from the single UP measurement.  How many people
>> observe it is irrelevant.  They're all in one world.
>>
>> The amplitudes still dictate relative frequencies, just as they do in
>> standard QM. The mechanism isn’t imposed externally—it’s in the structure
>> of the wavefunction itself. You ask what equation determines that branches
>> aren’t uniform: the answer is the same equation that governs quantum
>> amplitudes. The measure of an outcome isn’t arbitrary—it follows from the
>> squared amplitude of that outcome, just as it does in any quantum
>> experiment.
>>
>> Here you spend three sentences to say the Born rule is instantiated.  But
>> why and how is nothing but assertion and hand waving.  Bruce and I have
>> both challenged you to provide the mathematics.  You say the equation that
>> governs quantum amplitudes.  But in an SG experiment the probability
>> amplitude for UP is proportional to cos(phi) where phi is the angle between
>> the beam

Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

I’m not just repeating that the Born rule works—I’m pointing out that any
valid interpretation must explain why it works. You keep arguing as if I’m
assuming it, but the argument is that measure provides a natural way to
account for it without assuming it outright.

The lottery analogy illustrates this: more copies of an observer in a
high-measure branch means an observer is overwhelmingly likely to
experience that outcome. This is not about assuming the Born rule—it’s
about showing how a distribution naturally arises from the structure of the
wavefunction.

You seem to interpret "more observers" as meaning entirely separate people
in the same world. That’s not what’s being said. If the wavefunction
remains a continuous superposition, then what we call "a branch" isn’t a
single, discrete entity—it’s a coarse partition in an underlying structure.
More observers in a branch means more instances of the same observer, not
more independent individuals.

If you think this fails to explain the Born rule, then the burden is on you
to show why. Just stating that the Schrödinger equation doesn’t explicitly
derive it ignores the fact that all interpretations rely on additional
reasoning to connect math to experience. Dismissing this as "assuming what
needs to be proven" without engaging with how measure distributes observer
instances doesn’t resolve anything.

Quentin

Le ven. 21 févr. 2025, 22:59, Brent Meeker  a écrit :

>
>
> On 2/20/2025 11:30 PM, Quentin Anciaux wrote:
>
> Brent,
>
> The Schroedinger equation governs the evolution of the wavefunction, but
> decoherence determines the effective structure of branches.
>
> A branch is defined the result of the measurement.  If the electron spin
> is UP, then that defined the UP branch.  Decoherence presumably spreads
> from the SG detector and makes a world around UP that's orthogonal to the
> world around DWN.  "Effective structure" beyond this is just your invention.
>
> When I say a branch isn’t a single discrete unit, I mean that what we call
> a “branch” is an approximation—a macroscopic, emergent structure from the
> underlying quantum evolution.
>
> Why isn't it single in the sense that it is the branch that originated
> from a single measurement value.  "emergent structure from the underlying
> quantum evolution" is just obfuscation.
>
> The wavefunction never truly “splits” into countable, independent worlds;
> rather, it evolves into a superposition of decohered, non-interfering
> components, which we approximate as separate branches.
>
> If they are non-interfering they are in a superposition.  They're
> orthogonal.
>
>
> The fact that different results are orthogonal doesn’t mean each result
> corresponds to exactly one observer copy.
>
> The UP world originated from the single UP measurement.  How many people
> observe it is irrelevant.  They're all in one world.
>
> The amplitudes still dictate relative frequencies, just as they do in
> standard QM. The mechanism isn’t imposed externally—it’s in the structure
> of the wavefunction itself. You ask what equation determines that branches
> aren’t uniform: the answer is the same equation that governs quantum
> amplitudes. The measure of an outcome isn’t arbitrary—it follows from the
> squared amplitude of that outcome, just as it does in any quantum
> experiment.
>
> Here you spend three sentences to say the Born rule is instantiated.  But
> why and how is nothing but assertion and hand waving.  Bruce and I have
> both challenged you to provide the mathematics.  You say the equation that
> governs quantum amplitudes.  But in an SG experiment the probability
> amplitude for UP is proportional to cos(phi) where phi is the angle between
> the beam polarization and the instrument's "UP".  The electron however
> doesn't carry that information to the detector; the electron just registers
> on the counter as 0 or 1.  Which is Bruce's point that the "a" and "b" in
> a|up>+b|dwn> are NOT part of information available in the experimental
> record.  The structure of the wave-function just determines the sequence of
> 0s and 1s.  You know the answer you want, the Born rule, so you just
> suppose it must be in there somewhere.  But it's not as Bruce's example
> shows and also the many failures by smart people to try to derive the Born
> rule.
>
>
> Your example about performing an experiment in a Superbowl crowd vs. an
> undergrad lab misunderstands what’s being discussed. The measure isn’t
> about the number of classical humans performing an experiment—it’s about
> how many instances of an observer are instantiated in a given outcome due
> to the structure of the wavefunction.
>
> Yes, I know what you meant, I'm just cautioning you against using
> misleading language.  What you meant is the SG detector, when registering
> an electron UP instead of decoherence producing one UP-branch it produces a
> whole lot, a bush of UP-branches *and the number of branches in this bush
> is proportional the b^2 in Bruce's e

Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/20/2025 11:30 PM, Quentin Anciaux wrote:

Brent,

The Schroedinger equation governs the evolution of the wavefunction, 
but decoherence determines the effective structure of branches.
A branch is defined the result of the measurement.  If the electron spin 
is UP, then that defined the UP branch.  Decoherence presumably spreads 
from the SG detector and makes a world around UP that's orthogonal to 
the world around DWN.  "Effective structure" beyond this is just your 
invention.


When I say a branch isn’t a single discrete unit, I mean that what we 
call a “branch” is an approximation—a macroscopic, emergent structure 
from the underlying quantum evolution.
Why isn't it single in the sense that it is the branch that originated 
from a single measurement value.  "emergent structure from the 
underlying quantum evolution" is just obfuscation.


The wavefunction never truly “splits” into countable, independent 
worlds; rather, it evolves into a superposition of decohered, 
non-interfering components, which we approximate as separate branches.
If they are non-interfering they are in a superposition.  They're 
orthogonal.


The fact that different results are orthogonal doesn’t mean each 
result corresponds to exactly one observer copy.
The UP world originated from the single UP measurement.  How many people 
observe it is irrelevant.  They're all in one world.


The amplitudes still dictate relative frequencies, just as they do in 
standard QM. The mechanism isn’t imposed externally—it’s in the 
structure of the wavefunction itself. You ask what equation determines 
that branches aren’t uniform: the answer is the same equation that 
governs quantum amplitudes. The measure of an outcome isn’t 
arbitrary—it follows from the squared amplitude of that outcome, just 
as it does in any quantum experiment.
Here you spend three sentences to say the Born rule is instantiated.  
But why and how is nothing but assertion and hand waving.  Bruce and I 
have both challenged you to provide the mathematics.  You say the 
equation that governs quantum amplitudes. But in an SG experiment the 
probability amplitude for UP is proportional to cos(phi) where phi is 
the angle between the beam polarization and the instrument's "UP".  The 
electron however doesn't carry that information to the detector; the 
electron just registers on the counter as 0 or 1.  Which is Bruce's 
point that the "a" and "b" in a|up>+b|dwn> are NOT part of information 
available in the experimental record.  The structure of the 
wave-function just determines the sequence of 0s and 1s.  You know the 
answer you want, the Born rule, so you just suppose it must be in there 
somewhere.  But it's not as Bruce's example shows and also the many 
failures by smart people to try to derive the Born rule.




Your example about performing an experiment in a Superbowl crowd vs. 
an undergrad lab misunderstands what’s being discussed. The measure 
isn’t about the number of classical humans performing an 
experiment—it’s about how many instances of an observer are 
instantiated in a given outcome due to the structure of the wavefunction.
Yes, I know what you meant, I'm just cautioning you against using 
misleading language.  What you meant is the SG detector, when 
registering an electron UP instead of decoherence producing one 
UP-branch it produces a whole lot, a bush of UP-branches */and the 
number of branches in this bush is proportional the b^2 in Bruce's 
example./*  It's this last that is the problem. There is no mechanism 
for it.  It is just your gratuitous assumption to get the Born rule by 
branch counting.


The classical analogy would be a lottery where some numbers are 
printed in greater quantities than others; if you pick a ticket 
randomly, you are overwhelmingly likely to pick a more common one.


If branch count alone determined probability, we wouldn’t see Born’s 
rule in experiments.
We would if you just assume the right number of branches.  But as JKC 
pointed out, doing so requires retro-causation to change the past.


Since we do, that means any valid interpretation of QM must account 
for why low-amplitude branches contribute less to observer 
experiences. If you believe MWI fails to do this, then you need to 
provide a counterargument that doesn’t assume what it wants to 
prove—that all branches contribute equally regardless of amplitude.
You are the one claiming that the Born rule follows from the 
Schroedinger equation.  Above you just repeat that we know it applies.  
Yes, we know it applies empirically and for more that two results is 
implied by Gleason's theorem.  But that's not a derivation or a proof.  
You just repeating you it must be so because we know it workds doesn't 
add anything.


Brent

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T

Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

The Born rule is not something that "should" be obeyed—it is obeyed in
experiments. The question is why. Saying "some things happen and others
don’t" doesn’t answer that. If amplitudes determine the behavior of quantum
systems in every other context, why would they suddenly become meaningless
when it comes to observer experiences? That’s what you need to justify.

You claim that talking about observers is "obfuscation," but probability
itself is about expectations—what an observer should expect to see given
the structure of the theory. If multiple observers look at the same SG
detector, yes, they all see UP. But why was that outcome observed with
probability a² rather than any other distribution? Ignoring that question
doesn’t make it go away.

The challenge for any interpretation—whether MWI, collapse, or anything
else—is to explain why experiments follow the Born rule. Dismissing the
problem as circular without engaging with why amplitudes might determine
observer frequencies is avoiding the issue, not resolving it.

Quentin

Le ven. 21 févr. 2025, 22:25, Brent Meeker  a écrit :

>
>
> On 2/20/2025 11:29 PM, Quentin Anciaux wrote:
>
> Bruce,
>
> The claim follows from basic probability reasoning applied to MWI.
> Decoherence ensures that branches evolve independently, preventing
> interference. This means that observer instances in different branches
> cannot interact. If you accept that observer experiences are determined by
> where they find themselves in the wavefunction, then the relative frequency
> of experiences should follow the distribution of amplitudes squared.
>
> "Should" why?  So that the Born rule will be obeyed, which is why your
> argument is circular.  And you keep talking about observers and their
> experience.  This is just obfuscation.  Once an electron spin is measured
> UP arbitrarily many observers can look at the SG detector film and
> experience seeing it up.  That has nothing to do with the Born rule.
>
> Brent
>
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Re: Why even physicists still don’t understand quantum theory 100 years on




On 2/20/2025 11:29 PM, Quentin Anciaux wrote:

Bruce,

The claim follows from basic probability reasoning applied to MWI. 
Decoherence ensures that branches evolve independently, preventing 
interference. This means that observer instances in different branches 
cannot interact. If you accept that observer experiences are 
determined by where they find themselves in the wavefunction, then the 
relative frequency of experiences should follow the distribution of 
amplitudes squared.
"Should" why?  So that the Born rule will be obeyed, which is why your 
argument is circular.  And you keep talking about observers and their 
experience.  This is just obfuscation.  Once an electron spin is 
measured UP arbitrarily many observers can look at the SG detector film 
and experience seeing it up.  That has nothing to do with the Born rule.


Brent

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Re: Why even physicists still don’t understand quantum theory 100 years on

2025-02-21 Thread John Clark

On Fri, Feb 21, 2025 at 12:39 AM Bruce Kellett 
wrote:

*>  a 'branch' encompasses the whole world, so if you want more than one
> person on each branch, you have the entire population of the world on each
> branch.*

*Yes.*

* > Unfortunately, the same population can be found on every branch, *

*Yes, but I don't see why you say that is "unfortunate".  *

*>so that does not give you the necessary partitioning according to branch
> weight.*

*One of you sees a live cat in the box and another of you sees a dead cat
in the box and each observation causes the world and everybody in it to
split; however unless those other people have interacted with you they will
not have changed. And two conscious brains that are identical is
indistinguishable from one both subjectively and objectively. And if
there's no subjective difference and there's no objective difference then
there is just no difference. *

*John K ClarkSee what's on my new list at  Extropolis
*
4ej

>

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Re: Why even physicists still don’t understand quantum theory 100 years on

Brent,

The Schroedinger equation governs the evolution of the wavefunction, but
decoherence determines the effective structure of branches. When I say a
branch isn’t a single discrete unit, I mean that what we call a “branch” is
an approximation—a macroscopic, emergent structure from the underlying
quantum evolution. The wavefunction never truly “splits” into countable,
independent worlds; rather, it evolves into a superposition of decohered,
non-interfering components, which we approximate as separate branches.

The fact that different results are orthogonal doesn’t mean each result
corresponds to exactly one observer copy. The amplitudes still dictate
relative frequencies, just as they do in standard QM. The mechanism isn’t
imposed externally—it’s in the structure of the wavefunction itself. You
ask what equation determines that branches aren’t uniform: the answer is
the same equation that governs quantum amplitudes. The measure of an
outcome isn’t arbitrary—it follows from the squared amplitude of that
outcome, just as it does in any quantum experiment.

Your example about performing an experiment in a Superbowl crowd vs. an
undergrad lab misunderstands what’s being discussed. The measure isn’t
about the number of classical humans performing an experiment—it’s about
how many instances of an observer are instantiated in a given outcome due
to the structure of the wavefunction. The classical analogy would be a
lottery where some numbers are printed in greater quantities than others;
if you pick a ticket randomly, you are overwhelmingly likely to pick a more
common one.

If branch count alone determined probability, we wouldn’t see Born’s rule
in experiments. Since we do, that means any valid interpretation of QM must
account for why low-amplitude branches contribute less to observer
experiences. If you believe MWI fails to do this, then you need to provide
a counterargument that doesn’t assume what it wants to prove—that all
branches contribute equally regardless of amplitude.

Quentin

Le ven. 21 févr. 2025, 07:16, Brent Meeker  a écrit :

>
>
> On 2/20/2025 9:48 PM, Quentin Anciaux wrote:
>
> Brent,
>
> The key point is that a branch isn’t a single, discrete unit—it’s a
> coarse-grained structure emerging from decoherence.
>
> It must emerge from the thing measured; from a discrete result.  There's
> no mechanism for creating a "coarse grained structure".
>
> The fact that a branch has "only one result" is an approximation because,
> in reality, the wavefunction remains a superposition of countless
> micro-branches.
>
> But they all agree on the measurement result; otherwise they would be a
> branch.
>
> What we call "a branch" is just a region where interference is negligible,
>
> ??  It's interference that eliminates the superposition of different
> results.
>
> but within that, there are still subtler partitions based on amplitude.
>
> Yes, observer instances are in orthogonal branches, but the partitioning
> isn’t uniform.
>
> Why not?  What mechanism, defined in what equation makes them not uniform,
> i.e. one per result.  I know you would like there to be mechanism, but that
> doesn't make it so; and it certainly doesn't make the Schroedinger equation
> that mechanism.
>
> The measure of a branch corresponds to the number of observer instances
> experiencing that outcome,
>
> So if I perform an experiment in from a Superbowl crowd my results will be
> more probable than those in undergrad lab on the 3rd floor of the physics
> building.
>
> not to the number of distinct sequences. This means that instead of "one
> observer per branch," there are exponentially more copies of an observer in
> high-amplitude branches than in low-amplitude ones.
>
> The difference is subtle but crucial: If you assume one observer per
> branch, you get branch counting and no Born rule. But if you recognize that
> branches are not discrete and observer instances scale with measure, you
> naturally recover Born probabilities.
>
> Do you?  Let's see you do that math.
>
> Brent
>
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Re: Why even physicists still don’t understand quantum theory 100 years on

Bruce,

If you are so certain that MWI is inconsistent with the Born rule, then the
logical step would be to publish a formal refutation. If your argument is
as definitive as you claim, it would resolve one of the longest-standing
debates in quantum foundations, earning you the recognition you deserve.
Yet, instead of engaging with the actual research on the subject, you
dismiss any attempt at derivation as “unjustified nonsense” without
addressing the core issue.

You keep demanding extraordinary evidence while assuming as fact that
branch counting is correct and that amplitudes have no effect on observer
distribution. But that’s precisely what is in question. You haven’t
demonstrated why unitary evolution should treat all branches equally when
quantum mechanics itself does not. Amplitudes matter in every quantum
process—why would they suddenly become irrelevant when it comes to observer
experiences?

I’m not claiming that the issue is fully resolved, but pretending that it’s
settled in your favor without actually proving it is just posturing. If
your position is as airtight as you insist, why not take it to the academic
community instead of repeating the same assertions here?

Quentin

Le ven. 21 févr. 2025, 09:18, Bruce Kellett  a
écrit :

> On Fri, Feb 21, 2025 at 6:29 PM Quentin Anciaux 
> wrote:
>
>> Bruce,
>>
>> The claim follows from basic probability reasoning applied to MWI.
>> Decoherence ensures that branches evolve independently, preventing
>> interference. This means that observer instances in different branches
>> cannot interact. If you accept that observer experiences are determined by
>> where they find themselves in the wavefunction, then the relative frequency
>> of experiences should follow the distribution of amplitudes squared.
>>
>
> That is an assumption that has never been shown to be true.
>
> The justification is straightforward: if there are exponentially more
>> observers in high-amplitude branches than in low-amplitude ones, then a
>> randomly selected observer will overwhelmingly find themselves in a
>> high-measure branch. This is not an additional assumption—it follows
>> directly from the structure of unitary evolution.
>>
>
> No, it does not follow from unitary evolution. It follows from your
> unjustified assumption that there are exponentially more observers in
> high-amplitude branches than in low-amplitude ones. Talk about claims that
> need to be justified. This stands out as an extraordinary claim.
>
> Your argument assumes that every sequence contributes equally to
>> probability estimation, but that assumption is precisely what is in
>> question. You are treating "branches" as discrete, countable objects,
>> rather than as partitions of a continuously evolving wavefunction.
>>
>
> That is just unjustified nonsense. You have not proved anything like this.
>
> The fact that decoherence prevents recombination does not mean each branch
>> carries equal measure in terms of observer experience.
>>
>> If you believe otherwise, then you need to justify why amplitudes, which
>> govern all other quantum phenomena, should suddenly become irrelevant in
>> determining observer distribution.
>>
>
> You are the one making extraordinary claims, and extraordinary claims
> require extraordinary evidence -- which is not forthcoming.
>
> Bruce
>
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Re: Why even physicists still don’t understand quantum theory 100 years on

On Fri, Feb 21, 2025 at 5:16 PM Brent Meeker  wrote:

Brent,

This is beginning to sound like an argument we had with someone on another
list. His final position in that case was that, although he could not give
comprehensive arguments for his contentions, it had to be that way if his
theory was correct.

This is precisely where Quentin is currently. He keeps making extrordinary
claims without any shred of justification -- because if these claimds are
not so then his theory is in trouble.

The simplest conclusion is that his theory is not correct.

Bruce

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Re: Why even physicists still don’t understand quantum theory 100 years on