Joe Henson rediscovers Rovelli Smerlak (dropping ontic definiteness assumption)

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marcus
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Joe Henson posted a beautiful paper today which is also curiously reminiscent of the 2006 Rovelli Smerlak paper "Relational EPR".

In 2006, to resolve troubling paradoxes, R&S proposed relaxing the assumption of "strict Einstein realism"
(an absolute observerindependent ontology: a complete definite Reality that, however, only a kind of super-observer could appreciate.)

In a somewhat similar way, also to resolve paradoxes, Henson proposes to relax the assumption of ontic definiteness: that all statements about the universe can simultaneously be given truth values. Ontic definiteness attributes to Existence, or to Reality, a feature which only a superbeing could appreciate: The idea that definite answers to all questions exist, in an absolute observerindependent sense, even though we mortals cannot know them.

Henson's paper is (from my perspective) deep, and finely argued. It takes me into new territory. And it also, as I said, reminds me strongly of R&S "Relational EPR".

Here is Henson's paper:
http://arxiv.org/abs/1102.2855
Causality, Bell's theorem, and Ontic Definiteness
Joe Henson
40 pages (26 main text), 3 figures
(Submitted on 14 Feb 2011)
"Bell's theorem shows that the reasonable relativistic causal principle known as 'local causality' is not compatible with the predictions of quantum mechanics. It is not possible maintain a satisfying causal principle of this type while dropping any of the better-known assumptions of Bell's theorem. However, another assumption of Bell's theorem is the use of classical logic. One part of this assumption is the principle of 'ontic definiteness', that is, that it must in principle be possible to assign definite truth values to all propositions treated in the theory. Once the logical setting is clarified somewhat, it can be seen that rejecting this principle does not in any way undermine the type of causal principle used by Bell. Without ontic definiteness, the deterministic causal condition known as Einstein Locality succeeds in banning superluminal influence (including signalling) whilst allowing correlations that violate Bell's inequalities. Objections to altering logic, and the consequences for operational and realistic viewpoints, are also addressed."

I must say that personally I find it easy to reliquish the assumption of ontic definiteness and indeed am not certain I ever adhered to it. :biggrin:
 
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marcus
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Here is the Rovelli Smerlak paper. We had a lively thread about it back in 2006 here at PF Beyond forum.

http://arxiv.org/abs/quant-ph/0604064
Relational EPR
Matteo Smerlak, Carlo Rovelli
Foundations of Physics vol. 37 pages 427-445 (2007)
(Submitted on 10 Apr 2006)
We study the EPR-type correlations from the perspective of the relational interpretation of quantum mechanics. We argue that these correlations do not entail any form of 'non-locality', when viewed in the context of this interpretation. The abandonment of strict Einstein realism implied by the relational stance permits to reconcile quantum mechanics, completeness, (operationally defined) separability, and locality."

The abandonment of strict Einstein realism was what gave them the elbow room they needed.
 
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Its hard to get my head around this paper what does Hanson exactly mean with this, strip quantum mechanics of it's spookines non-locality entanglement and so on

Alinea A.3 intriques me, only its hard for an amateur to really make deep sense of it..
 
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apeiron
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I must say that personally I find it easy to reliquish the assumption of ontic definiteness and indeed am not certain I ever adhered to it. :biggrin:
Yes, it is certainly nice seeing people coming round to a logic of vagueness. Or embracing the principle of ontic indefiniteness.
 
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ConradDJ
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Joe Henson posted a beautiful paper today which is also curiously reminiscent of the 2006 Rovelli Smerlak paper "Relational EPR".

In 2006, to resolve troubling paradoxes, R&S proposed relaxing the assumption of "strict Einstein realism" (an absolute observer independent ontology: a complete definite Reality that, however, only a kind of super-observer could appreciate.)

In a somewhat similar way, also to resolve paradoxes, Henson proposes to relax the assumption of ontic definiteness: that all statements about the universe can simultaneously be given truth values. Ontic definiteness attributes to Existence, or to Reality, a feature which only a superbeing could appreciate: The idea that definite answers to all questions exist, in an absolute observer independent sense, even though we mortals cannot know them.

Marcus, thanks for pointing out this paper. I would agree that the “ontic definiteness” assumption is the big obstacle to understanding QM. And Henson does disentangle it from a bunch of related assumptions that have been mixed together in the EPR debates.

What’s very odd about this, to me, is that he treats it as an issue of logic, where the Rovelli Smerlak paper the issue is based on the physical approach of Relational QM.

To attempt a paraphrase – we tend to assume that there must be facts about everything, all the time. But evidence shows that in the case of an electron orbiting an atom, for example, there is no “fact” about its momentum or location... until one gets created by a physical interaction that defines and communicates that information.

If we treat “ontic definiteness” as a matter of logic, we can be more comfortable perhaps about QM. But we still have to address the physical issue of how there get to be facts in the world, and why “classical logic” works so well at the macroscopic level.

To me the value of Relational QM is that it sets up these questions. Since experiment shows that systems have definite states to the extent that those states are physically “meaningful” to other systems – that could prompt us to ask, what does it take to do this? In what kind of interaction-system can information about a system be “observed” by another system?

If it's true that all the information in the physical world is communicated information, then we do need to drop "ontic definiteness" as a basic assumption... but this is not just a logical move to resolve a logical paradox.
 
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marcus
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Conrad, I'm the one who owes you thanks. I feel stretched too thin right now and as if I can't risk delving into this. Back in 2006 when a bunch of us here at the forum got interested in the Rovelli Smerlak "Relational EPR" paper it was intriguing and absorbing.
I'm not ready for a second go-round of that.

But I was hoping very much that there would be someone to whom Henson's paper means something and who would be willing to comment.
 
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apeiron
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What’s very odd about this, to me, is that he treats it as an issue of logic, where the Rovelli Smerlak paper the issue is based on the physical approach of Relational QM.
My reading was that Henson probably favours the physical reality of ontic indefiniteness. In the note on p19 he says....

There seem to be two ways of thinking here. We can think of the basic truth valuations ontologically, in which case we might be tempted to say that the intermediate events in the basic truth valuations are “indefinite in reality”, i.e. that the truth value 1/2 as it appears in the basic truth valuations is ontologically distinct from 0 and 1. On the other hand, we can think of them epistemically, in which case we reject the idea that there are is anything like an ontic history at all, and give up the idea of the basic truth valuations as possible “mirrors of reality” (something similar to Dummet’s “antirealism” position), in which case we may prefer to say “unknown” rather than “indefinite”. The distinction can be made – or considered meaningless – according to the taste of the reader as it has no effect on any of the following arguments.
So it works either way - you can embrace indefiniteness as a real state. Or you can just treat it as a formal statement (because we can't really know what is real). But the second option has just as difficult consequences for other things you might want to believe in.

It is worth stepping back and thinking what a "logic" is. I would suggest it is a general model of causality - why things happen. QM conflicts with one familiar model, so we should look for other models. And softening the law of the excluded middle is a common tactic.

So I agree with Henson that this is an issue to be tackled at the level of logic. But that does not also make it an issue of what we take to be real.

Since experiment shows that systems have definite states to the extent that those states are physically “meaningful” to other systems – that could prompt us to ask, what does it take to do this?
We've discussed this before. But anyway my answer would be based on a dissipative structure theory approach.

Rather than trying to locate observers at particular points within the universe, I would make the whole universe an observing structure. And the interaction is between this structure, this classical history of definite events, and any remaining indefiniteness in the form of QM uncertainty.

So uncertainty - ontic indefiniteness - is the "stuff" that gets dissipated. When the universe was hot and small, there was a lot of dissipation to do. Now things are pretty cold and large, the action is residual.

You could still describe this dissipative structure as an ensemble of observers This would be just an atomised way of looking at the same thing. But what such an approach misses is the hierarchical organisation - the fact observation is spread over all scales, follows an asymptotic trajectory of dissipation, etc. There are some mathematical handles on the notion of "observation" that come from taking the macroscale systems view.
 

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