Wavefunction Realism vs Space-Time State realism

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David

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Oct 7, 2012, 2:54:57 AM10/7/12
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I was just reading some of the chapters from the upcoming book "The Wavefunction" by David Z. Albert where several different authors make their case for/against wavefunction realism and discuss the ontology of the WF in general.

We all know that the Everettian interpretation is very much "The WF is all there is", but David Wallace and Chris Timpson think that the standard "WF realism" is untenable and that itshould be replaced by space-time state realism. 
I was just wondering: which view is the fungible worlds ?

David Deutsch

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Oct 7, 2012, 4:25:54 AM10/7/12
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On 7 Oct 2012, at 07:54, David <davids...@gmail.com> wrote:

> I was just reading some of the chapters from the upcoming book "The Wavefunction" by David Z. Albert where several different authors make their case for/against wavefunction realism and discuss the ontology of the WF in general.
>
> We all know that the Everettian interpretation is very much "The WF is all there is", but David Wallace and Chris Timpson think that the standard "WF realism" is untenable and that it should be replaced by space-time state realism.
> I was just wondering: which view is the fungible worlds ?

I haven't read Albert's book, nor the Wallace-Timpson argument you're referring to. So I don't know what exactly they mean by 'wave function realism' or 'space-time state realism'.

But in any case, 'wave function realism' must be a telescoped term. "The wave function is real", though often used as a slogan to express realism in quantum theory, can't literally mean that reality consists of a certain function (a mapping from some exponentially large configuration space to the complex numbers). To make any sense, it must refer to the view that every mathematical property of the wave function (to be exact: every property except the overall phase) describes, or corresponds to, some property of the real, physical world.

All forms of the Everett interpretation (and also one half of the Bohm-interpretation equivocation) agree on that.

However, the wave function is a mathematical object used in the Schrödinger picture, in which information flow, and hence the structure of the multiverse, is expressed in a highly indirect, implicit way that has caused endless misunderstanding, especially the myth of quantum non-locality. In the Heisenberg picture, in which information flow is represented explicitly, it is manifestly local too. The state of the Heisenberg observables is then what corresponds to reality, and they are local functions on space-time. If that's what's meant by space-time realism, I'm all for it.

Fungibility is part of my attempt to explain what the multiverse is actually like, and should therefore be picture-independent.

-- David Deutsch






Alan Forrester

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Oct 7, 2012, 7:14:41 AM10/7/12
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Space-time state realism means the Schrodinger picture, with states associated with regions of spacetime, see Section 6 of

http://philsci-archive.pitt.edu/4621/1/ststaterealism.pdf

The authors endorse the idea that the Schrodinger state implies that reality is non-separable, i.e. that you can't work out the state of two regions by looking at the state of each region in isolation.

Alan

David

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Oct 7, 2012, 12:09:47 PM10/7/12
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However, the wave function is a mathematical object used in the Schrödinger picture, in which information flow, and hence the structure of the multiverse, is expressed in a highly indirect, implicit way that has caused endless misunderstanding, especially the myth of quantum non-locality. In the Heisenberg picture, in which information flow is represented explicitly, it is manifestly local too. The state of the Heisenberg observables is then what corresponds to reality, and they are local functions on space-time. If that's what's meant by space-time realism, I'm all for it.

Like Alan Forrester came to conclude: they reject the Heisenberg picture. If I remember correctly they also wrote a paper (Wallace and Timpson) against your and Hayden's approach to a local QM.
 
Fungibility is part of my attempt to explain what the multiverse is actually like, and should therefore be picture-independent.

If it's picture-independent then maybe it could work the way they've outlined after all ? hmm.
 

David Deutsch

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Oct 7, 2012, 1:29:45 PM10/7/12
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On 7 Oct 2012, at 17:09, David <davids...@gmail.com> wrote:

However, the wave function is a mathematical object used in the Schrödinger picture, in which information flow, and hence the structure of the multiverse, is expressed in a highly indirect, implicit way that has caused endless misunderstanding, especially the myth of quantum non-locality. In the Heisenberg picture, in which information flow is represented explicitly, it is manifestly local too. The state of the Heisenberg observables is then what corresponds to reality, and they are local functions on space-time. If that's what's meant by space-time realism, I'm all for it.

Like Alan Forrester came to conclude: they reject the Heisenberg picture.

One can't reject the Heisenberg picture, any more than one can reject long division. It's a technique. One can just decide not to use it. And one can confuse oneself as a result.

If I remember correctly they also wrote a paper (Wallace and Timpson) against your and Hayden's approach to a local QM.

Yes. They were mistaken. http://arxiv.org/abs/1109.6223

-- David Deutsch

David

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Oct 18, 2012, 1:28:28 AM10/18/12
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I want to reopen this question as I re-read their paper and it says clearly that it is picture independent so I am not sure why Alan Forester thought it was exclusively one or the other.

Regarding what you said: 

Yes. They were mistaken. http://arxiv.org/abs/1109.6223


Have you spoken to either of them regarding this paper? Do they now agree with you on it?

Also back on topic: in Wallace-Timpson the wavefunction does not live in configuration space, is this the same as in your fungible view?

john w Shaw

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May 24, 2016, 12:21:30 PM5/24/16
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Quantum Reality is of such a different order to human reality that I doubt we can ever have a vocabulary which will enable us to fully  comprehend or understand quantum reality. It is this human inability to go beyond the limitations our own perception which create the barrier to our accepting and making sense of this alternative but actual reality. John.

Alan Forrester

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May 24, 2016, 3:10:05 PM5/24/16
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On 24 May 2016, at 17:14, 'john w Shaw' via Beginning of Infinity <beginning-...@googlegroups.com> wrote:

Quantum Reality is of such a different order to human reality that I doubt we can ever have a vocabulary which will enable us to fully  comprehend or understand quantum reality. It is this human inability to go beyond the limitations our own perception which create the barrier to our accepting and making sense of this alternative but actual reality. John.

Your idea that quantum mechanics is incomprehensible is refuted in Chapter 11 of a book called "The Beginning of Infinity”. You might want to read it.

Alan

john w Shaw

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May 24, 2016, 6:28:50 PM5/24/16
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Thanks Allan I will have a look, John.

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