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Lee Smolin Real Ensemble I. questions

  1. Nov 6, 2013 #1


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    "Abstract: A new ensemble interpretation of quantum mechanics is proposed according to which the ensemble associated to a quantum state really exists: it is the ensemble of all the systems in the same quantum state in the universe. Individual systems within the ensemble have microscopic states, described by beables. The probabilities of quantum theory turn out to be just ordinary relative frequencies probabilities in these ensembles. Laws for the evolution of the beables of individual systems are given such that their ensemble relative frequencies evolve in a way that reproduces the predictions of quantum mechanics. These laws are highly non-local and involve a new kind of interaction between the members of an ensemble that define a quantum state. These include a stochastic process by which individual systems copy the beables of other systems in the ensembles of which they are a member. The probabilities for these copy processes do not depend on where the systems are in space, but do depend on the distribution of beables in the ensemble. Macroscopic systems then are distinguished by being large and complex enough that they have no copies in the universe. They then cannot evolve by the copy law, and hence do not evolve stochastically according to quantum dynamics. This implies novel departures from quantum mechanics for systems in quantum states that can be expected to have few copies in the universe. At the same time, we are able to argue that the centre of masses of large macroscopic systems do satisfy Newton’s laws."


    What do you think of it? I first read it in his book "Time Reborn" and found out there is a peer reviewed paper about it? Do you think it's possible? or unlikely (and why?)
  2. jcsd
  3. Nov 6, 2013 #2
    I was under the impression that a realistic reading of ensembles (e.g. an ensemble of ontic states) is ruled out as a result of the PBR theorem:
    On the reality of the quantum state

    This theorem attempts to rule out ψ-epistemic models, where quantum states are epistemic and there is some underlying ontic state so that quantum mechanics is the statistical theory of these ontic states. On the other hand, if one interprets the quantum state as representing information about possible measurement outcomes and not about the objective physical state of the system, this would violate one of the assumptions of the PBR theorem and would not be affected by PBR. Two experiments have been done confirming QT:
    Can different quantum state vectors correspond to the same physical state? An experimental test
    Experimentally probing the reality of the quantum state

    Am I mistaken in my interpretation of all of this stuff?
  4. Nov 7, 2013 #3


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    The Smolin's theory is not in contradiction with the PBR theorem. According to the PBR theorem, it is possible that wave function is not fundamental, and yet that from the fundamental ontic degrees of freedom one can determine an emergent effective wave function. The Smolin's theory is of that kind.

    In other words, the PBR theorem does not claim that psi is not epistemic. Instead, it claims that psi is not ONLY epistemic. That is, for practical purposes one may well use psi for epistemic purposes (as is done, e.g., in quantum information theory), but fundamentally it must somehow be encoded in the fundamental ontic degrees of freedom.
    Last edited: Nov 7, 2013
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