> On 26 Jul 2018, at 23:37, agrayson2...@gmail.com wrote:
>
>
>
> On Thursday, July 26, 2018 at 4:59:01 PM UTC, Bruno Marchal wrote:
>
>> On 26 Jul 2018, at 09:55, agrays...@gmail.com <javascript:> 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.
>
> |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. 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
>
>
>
>
>
>
>
>
>
>
>
>>> 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. AG
>>
>> 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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