Can a model exist that is local yet realistic in quantum mechanics?

  • Context: Graduate 
  • Thread starter Thread starter maline
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the possibility of a model in quantum mechanics that is both local and realistic. Participants explore various interpretations and models, including Many Worlds and ignorance ensemble interpretations, while questioning how these frameworks address the implications of measurement choices on distant outcomes.

Discussion Character

  • Debate/contested
  • Exploratory
  • Conceptual clarification

Main Points Raised

  • Some participants assert that Bell & Aspect's work demonstrates the impossibility of local realism, while Bohm's model is cited as realistic but non-local.
  • Many Worlds is proposed as a local but not realistic interpretation, with some arguing that it does not exclude future contexts from influencing present measurements.
  • The ignorance ensemble interpretation is mentioned as typically considered local and not realistic, though some participants express differing views on its classification.
  • One participant notes that Many Worlds can evade Bell's theorem by being non-counterfactual definite, complicating its classification as real.
  • Another participant introduces a model suggesting that only observers are real, while the observed objects are not, but acknowledges that this model may still exhibit slight non-locality.
  • Concerns are raised about the unpredictability of which "world" one finds oneself in within Many Worlds, leading to discussions about counterfactual definiteness and its implications for interpretations like EPR.

Areas of Agreement / Disagreement

Participants express a range of views on the classification of interpretations and models, indicating that there is no consensus on whether a local yet realistic model can exist. Disagreements persist regarding the implications of various interpretations on locality and realism.

Contextual Notes

Some interpretations are described as having nuanced classifications that depend on individual perspectives, and there are unresolved questions about the implications of locality and realism in quantum mechanics.

maline
Messages
436
Reaction score
69
Bell & Aspect proved you can't have local realism. Bohm set up a model that is realistic but not local. Is there a meaningful model that is local but not realistic? How would it explain the way measurement choices affect distant outcomes?
 
  • Like
Likes   Reactions: 1 person
Physics news on Phys.org
maline said:
Bell & Aspect proved you can't have local realism. Bohm set up a model that is realistic but not local. Is there a meaningful model that is local but not realistic? How would it explain the way measurement choices affect distant outcomes?

There are a number of interpretations that are local but not realistic in the usual sense. Not all people classify these the same as I, but here are a couple:

- Many Worlds

- Time Symmetric/Retro-causal/Block world - these do not not exclude future setup/context from contributing to the present. The answer to the question of "where are the hidden variables": in the future.
 
maline said:
Bell & Aspect proved you can't have local realism. Bohm set up a model that is realistic but not local. Is there a meaningful model that is local but not realistic? How would it explain the way measurement choices affect distant outcomes?

The ignorance ensemble interpretation is usually considered local and not realistic - although that would not be my classification. The issue of locality depends on your view of the status of breaking entanglement when entanglement is simply a mathematical device to describe correlations. I personally don't look at it that way and say its both non local and not realistic - but opinions vary.

As you can see, and as Dr Chinese correctly pointed out, not everyone classifys things the same way. Many would classify MW as real because the only thing that exists in it is the universal wavefunction that is as real as they come - in that interpretation that is. So how does MW evade Bell? Its not counterfactual definite - you can't predict the outcome of observations. It's subtle like a lot of this stuff.

The other day I was trying to think of a theory that is real but not couterfactual definite - MW was the only one I could think of and even that required a bit of thought and reading of some literature.

Thanks
Bill
 
Last edited:
In many worlds the worlds " can " be infinity worlds but some of them colapst by the viewer , and the numbers of the many world depend on stabilizesion on the viewer , so in bell when you check one side , it stabilize , colapst and afect on the ather side . It come from mulltiply worlds to feu and it some kind of geometry for the particle
 
maline said:
Bell & Aspect proved you can't have local realism. Bohm set up a model that is realistic but not local. Is there a meaningful model that is local but not realistic? How would it explain the way measurement choices affect distant outcomes?
See e.g.
http://lanl.arxiv.org/abs/1112.2034 [Int. J. Quantum Inf. 10 (2012) 1241016]
which represents a model in which only observers are real, while the observed objects are not.
 
Water nosfim said:
In many worlds the worlds " can " be infinity worlds but some of them colapst by the viewer , and the numbers of the many world depend on stabilizesion on the viewer , so in bell when you check one side , it stabilize , colapst and afect on the ather side . It come from mulltiply worlds to feu and it some kind of geometry for the particle

I don't know what you mean.

But the situation in MW is that after decoherence, which is a purely quantum process, each outcome of an observation in the mixed state that results from decoherence, is interpreted as a new world. Its entirely real because the wavefunction in that interpretation is real, its local because the wavefunction is local, however you can't predict which world you will find yourself in so its not couterfactual definite.

Thanks
Bill
 
You find yourself at the world you stabilize in , and it depend on the force you have use to fit in
 
bhobba said:
you can't predict which world you will find yourself in

Wouldn't the answer be "definitely both"? What's unpredictable there? and how doer this affect EPR?
 
Demystifier said:
See e.g.
http://lanl.arxiv.org/abs/1112.2034 [Int. J. Quantum Inf. 10 (2012) 1241016]
which represents a model in which only observers are real, while the observed objects are not.

Thanks, but according to the abstract this model is still slightly non-local
 
  • #10
maline said:
Wouldn't the answer be "definitely both"? What's unpredictable there? and how doer this affect EPR?

Yea - but how can you say which world you are in - you can't - because you are in all - it fails counterfactual definiteness.

Its subtle and a matter of semantic opinion. Semantics would have to be the silliest thing to argue about, so if you don't agree that's fine by me.

It doesn't affect EPR except as a possible example of an interpretation that is real, local but fails counterfactual definiteness.

Thanks
Bill
 
  • #11
maline said:
Thanks, but according to the abstract this model is still slightly non-local
Yes, but this "small" nonlocality appears only at small distances, not at large distances typical for the EPR experiments.
 

Similar threads

Undergrad Bell's theorem claimed to be refuted - paper published by EPL
  • · Replies 50 ·
2
Replies
50
Views
8K
High School Quantum entanglement and hidden variables
  • · Replies 7 ·
Replies
7
Views
3K
Graduate Mathematical formulation of local non-realism
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Big Bell Test Collaboration: Challenging Local Realism with Human Choices
  • · Replies 6 ·
Replies
6
Views
3K
Undergrad Cosmic Bell Test: 600 yr Old "Freedom of Choice" Loophole
  • · Replies 8 ·
Replies
8
Views
3K
Undergrad Bell tests: Changing detector settings "just before photon arrives"
  • · Replies 4 ·
Replies
4
Views
2K
Graduate Bell Test Violates Local Realism w/ Loophole-Free Electron Spins 1.3km Apart
  • · Replies 63 ·
3
Replies
63
Views
9K
Graduate Loophole-free test of local realism via Hardy's violation
  • · Replies 37 ·
2
Replies
37
Views
7K
Graduate Is non-locality a necessary consequence of the Bell theorem?
  • · Replies 17 ·
Replies
17
Views
2K
Graduate What does a local non-realistic theory look like?
  • · Replies 69 ·
3
Replies
69
Views
10K