On Friday, July 27, 2018 at 10:41:32 AM UTC, Bruno Marchal wrote:
>
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> On 26 Jul 2018, at 23:37, [email protected] <javascript:> wrote:
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> On Thursday, July 26, 2018 at 4:59:01 PM UTC, Bruno Marchal wrote:
>>
>>
>> On 26 Jul 2018, at 09:55, [email protected] wrote:
>>
>>
>> *I think this discussion is a waste of time. You can't even understand
>> why a classical wave which extends to infinity along an infinite plane
>> implies FTL,*
>>
>>
>> You are right. I can’t understand that. It makes absolutely no sense to
>> me. Wave, in physics, are the paragon of locality. It is a local
>> perturbation which “contagiates" its local neighbours.
>>
>
>
> *How can the amplitude get to infinity in all directions along a plane,
> unless, when created, there is instantaneous propagation? AG*
>
>
>
> That is solved in QM by having only square integral functions, which tends
> to zero on infinity.
> A classical wave with arbitrary high amplitude is an dubious physical
> reality. It belongs to math, where there is no FTL, given that there is no
> time and space in mathematics. You just cannot create such a wave in a
> physical universe. I would say.
>
*You don't know what a plane wave is. Like any wave, the amplitude varies
in time and is finite. But for a plane wave, the values, whatever they are,
extend on a plane to infinity, and the plane moves as a function of time
and the values change identically along the entire plane. Nothing to do
with square integral functions. AG*
>
> * |and you bring in collapse at every opportunity, even though I am
> not discussing it in this context. *
>
>>
>>
>> Were talking between QM. We must decide if we put the collapse axiom or
>> not as part of the theory. That’s the key point in all the discussion about
>> the nature of the superposition.
>>
>
>
> *That's really another issue, obviously an important issue, but I was not
> discussing it in the context of my critique of superposition. AG *
>
>
> I really don’t see how we can evade that discussion when discussing about
> the physical nature, or the ontological nature, of the superposition.
>
*You're so obsessed with Everett and the collapse issue, that you are
INCAPABLE of discussing my critique of the interpretation of superposition.
Everett, like Copenhagen, assumes the same about superposition -- that all
components exist physically and simultaneously -- which I argue against. AG*
> For me, only Everett QM makes sense. Copenhagen would make sense with some
> reasonable explanation for the Physical collapse, but nobody finds it, and
> we know now that it would entails FTL or non-realism, etc. Without
> collapse, no superposition ever disappear, but everything becomes smooth
> again, except for the perhaps showing mutiplication of histories and
> persons, but it is only shocking, not contradictory, and not as magical
> than instantaneous action at a distance.
>
> Bruno
>
>
>
>
>
>> Bruno
>>
>>
>>
>>
>> *Let's end this discussion. AG*
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>> *Finally, FWIW, the mystery of QM is its probability prediction, which is
>>> *different* from what one would expect classically. This is because the wf
>>> is complex, and because the probability is calculated by taking the
>>> norm-squared, one gets a different prediction for the interference, which
>>> manifests mathematically by the existence of cross terms. A*G
>>>
>>>
>>> Indeed, and the cross term invites us to take Feynman many path, or
>>> Dirac superposition as physical reality.
>>>
>>>
>>>
>>>
>>>
>>>> That has been verified directly and indirectly by molecular and atomic
>>>> physics, and even black hole and cosmology. It is not a question of
>>>> interpretation: it is a fact that a state like up+down will pass with
>>>> probability one a “polariser” (analyser) measuring in the base {up+down,
>>>> up-down}, and that is not the case for a mixture of up and down particles,
>>>> each of which pass with a probability 1/2.
>>>>
>>>> Before discussing any interpretation, we need to agree on the theory we
>>>> are using. I am discussing Everett theory, which is Copenhagen minus the
>>>> collapse postulate. Without the collapse postulate, no superposition ever
>>>> reducse into a singular state projection. That contradicts the quantum
>>>> linearity.
>>>>
>>>> Being a pure state like “up” is always relative to an instrument
>>>> measure. All state are superposition when develop in other bases, and
>>>> those
>>>> are real, we can test them. A state like up is really up’ + down’. That is
>>>> exploited in quantum computing, where some algorithm can superposed many
>>>> computations at once, and, despite we cannot observe each individual
>>>> result, we can test global information on all results, like "are they all
>>>> the same or different? or question of parity of results, etc.
>>>>
>>>> The so called “many-world” interpretation is just QM-without-collapse
>>>> taken seriously. No need to add some metaphysical world(s) here or there.
>>>> A
>>>> world can be defined by just any completion of a state that we can
>>>> measure,
>>>> but it is an open problem if that exists (except with mechanism: we have
>>>> good reason to disbelieve such worlds).
>>>>
>>>> The instrumentalist idea that the superposition are only tools to
>>>> calculate probabilities was inspiring a long time ago, but it does not
>>>> work. Nature confirms their physicalness, notably by testing the
>>>> observable
>>>> difference between mixed state and superposition. We can add hidden
>>>> variable, or Bohm’s Guiding particles Potential, but this has been shown
>>>> to
>>>> lead to FTL (even instantaneous) influence(*) and other magic things or to
>>>> many-worlds.
>>>>
>>>> In my opinion, you are just saying that the physical reality do not
>>>> obey Everett quantum mechanics, i.e. that some collapse occurs somewhere,
>>>> instantaneously.
>>>>
>>>
>>> *I never discussed collapse, one way or another. I just claim that there
>>> is apparently no justification for the Copenhagen(?) INTERPRETATION of
>>> superposition in QM. *
>>>
>>>
>>>
>>> It is a new axiom in the theory, before leading to any interpretation. I
>>> agree with you, the collapse is just a coquetry added to avoid being
>>> oneself and the (local) physical reality multiplied. But there is no
>>> experimental evidence for such a collapse, and it entails FTL,
>>> indeterminacy. With the SWE without collapse, the probabilities come only
>>> from the impossibility to know which branch of the universal wave we are
>>> in, like with mechanism we cannot know which computations support us. QM
>>> confirms Mechanism here.
>>>
>>>
>>>
>>>
>>> *I have asked for the justification many times, but no takers. *
>>>
>>>
>>> In this list, few people believe in a collapse.
>>>
>>>
>>>
>>> *I don't think they can justify it. Of course, generally, postulates are
>>> not amenable to justification, but in the case of superposition, the
>>> interpretation I object to has a unique property; it's never applied in a
>>> calculation! *
>>>
>>>
>>>
>>> That makes no sense. I can’t explain neither the two slits, nor the
>>> working of an interferometer, nor the hydrogen atom, nor anything, without
>>> the superposition principle. The collapse is never used, but the
>>> superposition is just a consequence of the fact that state are represented
>>> by wave, or by “vector” in a Hilbert space (which mainly a linear
>>> (vectorial) space with some scalar product).
>>>
>>>
>>>
>>> *It just creates contradictions.*
>>>
>>>
>>> Where?
>>>
>>>
>>>
>>> * Nor do I discuss Everett insofar as it's the dumbest theory I have
>>> ever heard or, or can imagine. *
>>>
>>>
>>> Everett theory is just the SWE. It is the addition of the collapse which
>>> is the “dumb” move, I would say.
>>>
>>> Bruno
>>>
>>>
>>>
>>>
>>>
>>> *AG*
>>>
>>>
>>>> In 1927 Einstein gave a simple thought experience, the one particle in
>>>> a sphere, and explain that if the collapse is physical, it has to violate
>>>> special relativity. Hs EPR paper is closer to an experimental treatment,
>>>> as
>>>> Bell has shown, and QM seems to be vindicate, so the choice is really
>>>> between many-worlds, or the abandon of special relativity (or the bandit
>>>> that QM says anything about the physical reality).
>>>>
>>>> Bruno
>>>>
>>>>
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>>>
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