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Barry Silverman


Registered: Sep 2006
Posts: 2

nks, quantum theory, and hidden variables

I have recently read that deterministic interpretations of quantum theory using "hidden variables" are now considered feasible (after decades of being considered untrue due to EPR paradoxes).

Has anyone attempted to use NKS to "simulate" quantum behavior in e.g. a two-slit interference experiment.

I would expect that a simplified "observer" object would be part of the system - in that information propogation from the system to the observer would also have to be part of the simulation.

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Old Post 09-12-2006 06:21 PM
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Jason Cawley
Wolfram Science Group
Phoenix, AZ USA

Registered: Aug 2003
Posts: 712

The conventional understanding has been that EPR rules out hidden variable theories, but that is not strictly correct, and it has been known for quite some time. What EPR shows is that you can't have a local, classical theory with hidden variables. You can get a consistent hidden variable theory if you drop locality, which e.g. David Bohm proposed.

More recently, David Deutsch has argued that you can keep local information and information transmission, as long as it isn't locally accessible (even in principle). Which is a relaxing of the amount of real non-locality needed to get a hidden variable theory to work. (Deutsch is himself a many-worlds QM guy, instead, but wants the locally inaccessible information point for other, QC reasons).

But none of it is at the level of conducting experiments, and nobody involved disputes the standard results of two slit. Nor does anyone involved think subjective models are the way forward - amateur philosophers go for that angle, not physicists.

NKS argues for what is in effect a hidden variables theory, with some discrete and deterministic underlying structure of which QM is an emergent, large scale property or coarse approximation. Since it proposes that space as we experience it is an emergent property of its underlying network, it is not committed to locality in that emergent space as a basic feature. Wolfram discusses the subject in the notes to the final sections of chapter 9. He acknowledges that as yet no one has succeeded in making a discrete generator for QM work, but thinks he has sketched enough to show how it might be done.

The basis requirements of such a theory have been known for decades and are reasonably simple. Anything that gives appropriate brownian motion plus the right interference statistics at the microlevel, can give standard QM at a macrolevel. (All of QFT is a somewhat taller order it is true). Smolin and Hooft have both used that in the past.

Everyone should keep in mind that all of this is speculative stuff. Our best current physical theory is QFT and it is not discrete as math, and its usual interpretion is in terms of probability. A fair number of pretty bright people are looking at various different ways of changing one or the other of those things, but so far they have not successfully done so.

I hope this helps.

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Old Post 09-12-2006 09:11 PM
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Barry Silverman


Registered: Sep 2006
Posts: 2

Thanks Jason,
I have already read a paper from Lee Smolin about hidden variables - but as you have said - it is presented in statistical mechanics, and not in some deterministic algroithmic form.

Has anyone expanded on Wolfram's original concept of emergent space/time, and invented a simplistic algorthmic model that "emulates" QFT for even the simplest experiments?


To find someone that has the requisite background in QFT and in cellular automata seems kind of daunting....


I guess that this is exactly Wolfram's point.

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Old Post 09-12-2006 09:57 PM
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Jason Cawley
Wolfram Science Group
Phoenix, AZ USA

Registered: Aug 2003
Posts: 712

Wolfram has the background for it and he is working on it, obviously. It is entirely "in silico" experimentation at this stage, just trying to get any reasonable dynamic network to show plausible features. Testing any of it against existing QFT models is not imminent, let alone testing it against experiment. Those are goals and not shirked as desirable, but we aren't remotely there yet.

I should add that it is already clear the effort will discover plenty of interesting graph theory, as a matter of pure math. Whether it ties in to fundamental physics in the way Wolfram hopes, who knows? Theorists can propose but nature disposes.

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Old Post 09-12-2006 11:05 PM
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