On 06 Nov 2014, at 10:23, [email protected] wrote:
On Monday, November 3, 2014 4:28:50 PM UTC, Bruno Marchal wrote:
On 03 Nov 2014, at 02:14, Bruce Kellett wrote:
> Bruno Marchal wrote:
>> On 01 Nov 2014, at 23:55, Bruce Kellett wrote:
>>> Bruno Marchal wrote:
>>>> This I find hard to buy. I like the MW notably because it
>>>> restores determinacy and locality in the 3p big "physical"
>>>> picture. In the MW theory, we can explain the violation of Bells
>>>> inequality, without using anything non local, or instantaneous.
>>>> I took Aspect experiment as a confirmation of the MW idea.
>>>
>>> This is not so obvious. MWI struggles to explain the violations of
>>> Bell's inequality. It can do so only in a very strained way, and
>>> that at the price of counterfactual definiteness. It seems to me
>>> that this price might be too high.
>>>
>> One argument for this is perhaps too simple: the SWE is local and
>> linear all by itself, so in the Hilbert space of the "universal
>> wave", there is no "action at a distance". This can be used, I
>> think, to reduce the question of counterfactual definiteness to the
>> question of the definiteness of the worlds themselves, and this is
>> not yet clear to me. Eventually we have to find the MW view of the
>> Kochen & Specker theorem, well, you may be right that this is not
>> obvious.
>> I will try to do this by myself, and get back if I succeed. I am
>> currently explaining (trying to explain to be sure) to a group of
>> students how to "reduce" all weirdness of quantum mechanics to only
>> one: "the parallel universes", but sometimes I do have a problem
>> with the very notion of "universe", which is rarely well defined,
>> if define at all. I have always the need to take into account that
>> we have a brain-base prejudice on the picture of the "whole", and I
>> think that counterfactual definiteness might be in that category.
>> Coming from computationalism, with the mind-body problem as
>> motivation, I am somehow prepared to stop believing in "universe".
>> Coherent sheaf of dreams, or first person plural sharable
>> computations, like the one with computationalism, does not have to
>> converge on well defined "universe(s) independent of us", so I am
>> not sure if the abandon of counterfactual definiteness would be a
>> so high price to me. Eventually it might even be welcome, as
>> computationalism might also forbid it, so ... well, I don't know.
>> If I succeed in explaining (to me and my students) Bell's
>> inequality in a purely local way (with many worlds, or better many
>> relative states (capable of perhaps NOT defining worlds, but only
>> coherent sharable experience), I will try to sum up the idea here.
>> Have you read Deutsch and Hayden paper on this? I know that is well
>> debated, but I have not yet found the time to read/understand the
>> critics.
>
> I had not read this paper, but I do not find the proposal
> convincing. Deutsch seems merely to point to the fact that one
> observes the correlation in a Bell-type experiment only after the
> classical transfer of information, just as in any other quantum-
> teleportation situation. This might be true, but it is not really an
> explanation of the correlations.
It seems to me that quantum mechanics explain well the correlations,
which are consequences of the linearity of the tensor product and of
the evolution. Bell, even EPR, assumed implicitly the uniqueness of
the outcome after a measurement.
In fact I challenge the people who believe in non locality to show me
an example, with a proof that there is non-locality, and this without
adding a collapse. I don't see how that could even be possible.
There's no reason for expecting we shall see a way for a frontier
problem that could feasibly be the most mind boggling least
intuition friendly puzzle every revealed in science. It's ok for
that to be the status. It is the right status if it is true and most
robust. The status can be "we can even make sense of what that
means...". Trying to throw an explanation at a hard fundamental
problem is a disaster. No problem was solved this way before.
Science isn't like the philosophers. Science will wait. Decades,
generations hundreds of years. Science would leave it there and rest
its head in scientific dignity than throw daft explanations at
profound problems.
From what I understand, I agree with you. But it is not so clear what
the disastrous explanation is. I guess you mean the non local collapse
of the wave. OK?
Bruno
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