
#235
Jan2013, 07:22 PM

Sci Advisor
PF Gold
P: 5,145

Although we have (hopefully) left discussion of the OP behind, I would like to add a comment about nonrealism. Nonrealism can take a variety of forms. The above is one. Another is seen in MWI, because our reality is not exclusive. Another is seen in timesymmetric interpretations. In those, causes are not required to precede effects. Which is a tacit assumption in most formulations of realism. 



#236
Jan2013, 09:26 PM

PF Gold
P: 670





#237
Jan2113, 01:28 AM

P: 50

Realism in Bell/EPR discussions amounts to "counterfactual definiteness". Counterfactual definiteness means being able to meaningfully speak of values of observables that weren't measured but would have been obtained had they been measured. One might add, even in the case where an incompatible observable was measured instead.
Now this is still vague. "Meaningfully speak of" needs to be clarified and what it means for Bell discussions is that such values that would have been obtained (but weren't) can be treated on a par with actual obtained values when doing statistical calculations. (One might add, even for statistical calculations as simple as tallying.) This at first sounds like a completely reasonable assumption until one realises that its more or less saying that even though pigs can't fly we can average in a supposed pig flying speed together with actual measured flying speeds of doves and swallows and expect our calculations to still produce reproducible averages :) 



#238
Jan2113, 01:36 AM

P: 95





#239
Jan2113, 11:05 AM

P: 724

This is a different scenario. In the first, we are discussing 1 world only, so with respect to this one world, prior to observation the states aren't real, since they don't belong to the observed classical reality. In the latter case, the states can be said to be real(defined as having fixed properties) that belong to the relevant world when an interaction is performed. But anyone can play this interpretational mumbo jumbo. The only reason it is accepted here, as with all other interpretations, is because of the rank of the author  Everett, Bohr, Bohm, T'Hooft, etc. If it weren't for the status of author, these 'interpretations' would have been right there with the "What the beep do we know?". So if we imagine that there are infinitely many worlds, our unreal states suddenly become real in a sense. But let's keep the assumptions minimal, even if doing so implies change. 



#240
Feb113, 05:31 PM

P: 50

I just read Gisin's paper "Nonrealism: Deep Thought or a soft Option" (http://arxiv.org/pdf/0901.4255v2.pdf). He doesn't seem to be aware of the interpretation of "realism" as meaning counterfactual definiteness and doesn't even discuss it. He misses entirely the fact that the probability distributions in his equation 1 are not well defined in the face of noncounterfactual definiteness.




#241
Feb113, 06:47 PM

Sci Advisor
PF Gold
P: 5,145





#242
Feb113, 08:40 PM

PF Gold
P: 670

I have trouble completely understanding what he means by this, to be honest. 



#243
Feb213, 01:27 AM

P: 50

I'm also half way through Joy Christians rebuttal http://arxiv.org/pdf/1301.1653.pdf and so far all I see is a lot of unconscious redefining of how probability works with lots of Clifford algebra thingies ("multivectors") sitting in equations that have the shape of actual statistical calculations but which otherwise have no justification because they aren't really statistical calculations. We would need some reason for entangled particles to follow Clifford algebra based statistical mechanisms like this instead of normal statistics which is back to square one as this Clifford stuff is really just the usual tensor product Hibert space QM stats in a different notation. In the same way that the usual tensor product stuff appears to be implying some sort of nonlocal connection, so too is this mathematically equivalent Clifford algebra stuff. 



#244
Feb213, 01:50 AM

P: 50

Ok I read Gisin's definition again and it seems that he is also unaware of that the propensity approach he is advocating ends up producing the same statistics as a deterministic approach (one of Arthur Fine's results)  this is all discussed for example in Redhead's book http://www.amazon.com/Incompleteness.../dp/0198249373




#245
Feb213, 04:24 AM

P: 50

FYI: Arthur Fine's paper http://www.citeulike.org/user/egcava...rticle/6011736 where he shows that going for models that conform to what Gisin seems to be saying his personal definition of realism is, are in fact no more general than a local hidden variable theory.




#246
Feb213, 06:50 AM

P: 50

Further subtle points about Fine's result http://www.jstor.org/stable/187655




#247
Feb313, 10:00 PM

PF Gold
P: 670





#248
Feb613, 05:00 AM

P: 50

Actually after completing Joy Christians latest paper I'm not convinced the math is correct, its seemingly based on a Clifford Algebra model of what the tensor product Hilbert Space formalism is saying but also contains some dodgey limits. Either its just plain wrong or if fixable at most just copies what the standard formalism already tells us without adding any real explanantion  why should the stats conform to the Clifford algebra based pseudostatistics based on a parallelized hypersphere ... if there isn't some nonlocal mechanism enforcing it?




#249
Feb813, 12:49 AM

Sci Advisor
P: 1,185

I haven't gone through this whole thread, so this paper by Richard Gill may have already been cited: http://arxiv.org/abs/1203.1504
IMO, this paper is a completely convincing demonstration that Christian's claims about Bell are vacuous. Christian has a reply paper, which IMO is as vacuous as his previous ones. Find it yourself if you care to. 



#250
Feb813, 10:22 AM

Mentor
P: 11,220

Yes, Gill's article has been discussed in this thread, beginning here:
http://www.physicsforums.com/showthr...59#post3804759 In fact, Gill himself chimed in: http://www.physicsforums.com/showthr...65#post3812865 



#251
Feb813, 11:40 AM

Sci Advisor
P: 1,185

But it seems not everyone is convinced.




#252
Feb813, 12:07 PM

PF Gold
P: 670

http://arxiv.org/pdf/1212.0953v1.pdf Also discussed here: Does Probability Come from Quantum Physics? http://www.sciencedaily.com/releases...0205151450.htm 


Register to reply 
Related Discussions  
Joy Christian's disproof of Bell  Quantum Physics  70  
Bell's Theorem and "Counterfactual Definiteness"  Quantum Physics  5  
"Christian Science"  General Discussion  1  
Why is the Wikipedia article about Bell's spaceship "paradox" disputed at all?  Special & General Relativity  109 