On Fri, Sep 27, 2019 at 11:22 AM 'Brent Meeker' via Everything List < [email protected]> wrote:
> On 9/26/2019 5:53 PM, Bruce Kellett wrote: > > On Fri, Sep 27, 2019 at 10:35 AM 'Brent Meeker' via Everything List < > [email protected]> wrote: > >> On 9/26/2019 5:01 PM, Lawrence Crowell wrote: >> >> On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote: >>> >>> It seems that nearly everyone on the list has a strong opinion >>> about Sean Carroll's new book, but has anyone other than me actually read >>> it? >>> >>> John K Clark >>> >> >> I have not read his book, but I have read his papers and the one he >> coauthored with Sebbens. I know what he has done. I am definitely agnostic >> about MWI as I am with all interpretations. Carroll and Sebens has though >> opened the door to a relationship between the Born rule and MWI, >> >> >> Didn't you read *Quantum Theory of the Classical: Quantum Jumps, Born’s >> Rule, and Objective Classical Reality via Quantum Darwinism *by Zurek. >> arXiv:1807.02092v1 [quant-ph] 5 Jul 2018 >> >> He derives the Born rule from what he calls "environment induced >> supersymmetry". >> >> *Emergence of the classical world from the quantum substrate of our >> Universe is a long-standing* >> *conundrum. I describe three insights into the transition from quantum to >> classical that are based* >> *on the recognition of the role of the environment. I begin with >> derivation of preferred sets of states* >> *that help define what exists - our everyday classical reality. They >> emerge as a result of breaking of* >> *the unitary symmetry of the Hilbert space which happens when the >> unitarity of quantum evolutions* >> *encounters nonlinearities inherent in the process of amplification – of >> replicating information. This* >> *derivation is accomplished without the usual tools of decoherence, and >> accounts for the appearance* >> *of quantum jumps and emergence of preferred pointer states consistent >> with those obtained via* >> *environment-induced superselection, or einselection. Pointer states >> obtained this way determine* >> *what can happen – define events – without appealing to Born’s rule for >> probabilities. Therefore, p k =* >> *|ψ k | 2 can be now deduced from the entanglement-assisted invariance, >> or envariance – a symmetry of* >> *entangled quantum states. With probabilities at hand one also gains new >> insights into foundations* >> *of quantum statistical physics. Moreover, one can now analyze >> information flows responsible for* >> *decoherence. These information flows explain how perception of objective >> classical reality arises from* >> *the quantum substrate: Effective amplification they represent accounts >> for the objective existence* >> *of the einselected states of macroscopic quantum systems through the >> redundancy of pointer state* >> *records in their environment – through quantum Darwinism.* >> >> Brent >> > > That paper, and others by Zurek, are the main reason I think that QM might > ultimately make sense. Zurek understands that entanglement with the > environment leads to essential non-unitary states. He concludes the above > paper with: > > "Everett's insight -- the realisation that relative states settle the > problem of collapse -- was the key to these developments. But it is > important to be careful in specifying what exactly we need from Everett and > his followers, and what can be left behind. There is no doubt that the > concept of relative states is crucial. Perhaps even more important is the > idea that one can apply quantum theory to anything -- that there is nothing > \ab initio\ classical. But the combination of these two ideas does not yet > force one to adopt a "Many Worlds Interpretation" in which all the branches > are equally real." > > > Zurek cites this paper by Haliwell where he writes: > > https://arxiv.org/pdf/quant-ph/9902008.pdf > > > *In this paper we have effectively shown that the decoherence condition is > a reflection of the information* > *storage capacity of the environment. That is, it is a lower limit on the > degree to which the histories may be fine-grained without the information > storage capacity of the environment being exceeded.* > > But I don't see how to use this limit on information to prune the MWI > branches. > I don't even know what this means! Decoherence goes on by unitary evolution, regardless of whether the environment can store the information or not. Decoherence has nothing to do with fine graining, or anything else we do. That is one of my main problems with the decoherent histories idea. It relies on this idea of fine or coarse graining, so it introduces the observer back into places where the observer must be irrelevant. I don't think Zurek's reference to Halliwell particularly endorses the decoherent histories approach. He says: "Previous studies of the records 'kept' by the environment were focussed on its effect on the state of the system, and not on their utility." So Halliwell's focus is orthogonal to the idea of quantum Darwinism. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLRw7BeRtiLtsy-h_s2HeW1djbx%3DvucXo0YSc_2whAAgrQ%40mail.gmail.com.
