On 9/27/2019 11:18 AM, Bruno Marchal wrote:
On 26 Sep 2019, at 02:32, 'Brent Meeker' via Everything List <[email protected] <mailto:[email protected]>> wrote:On 9/25/2019 8:28 AM, Bruno Marchal wrote:On 24 Sep 2019, at 17:44, Philip Thrift <[email protected] <mailto:[email protected]>> wrote:On Tuesday, September 24, 2019 at 6:23:10 AM UTC-5, Bruno Marchal wrote:On 24 Sep 2019, at 10:22, Philip Thrift <[email protected] <javascript:>> wrote: On Tuesday, September 24, 2019 at 3:05:39 AM UTC-5, Alan Grayson wrote: On Tuesday, September 24, 2019 at 1:36:42 AM UTC-6, Philip Thrift wrote: On Monday, September 23, 2019 at 8:44:39 PM UTC-5, Brent wrote: On 9/23/2019 6:24 PM, Alan Grayson wrote:On Monday, September 23, 2019 at 3:44:49 PM UTC-6, Brent wrote: On 9/23/2019 11:59 AM, Philip Thrift wrote:/But other quantum experts use decoherence to explain quantum phenomena without invoking multiple universes./"Without invoking" doesn't mean "denying". It does if you believe in applying Occam's Razor. AGTrue. But I'm still waiting for pt to quote this expert saying he explains quantum phenomena without MW. He keeps implying it's Zurek, but I just read Zurek's paper on quantum Darwinism again and ISTM Zurek is assuming MWI throughout. QD is just his solution to the basis problem. Brent Zurek is not on a book tour, nor does he tweet, but after the rollout of Carroll's book, one can only conclude: * Many Worlds is religion, not science.* @philipthrift Right. You'll notice how my comment that the MWI is tantamount to "hubris on steroids" was never responded to. Hopefully, he'll be denied tenure, and his book and personage can go into the dustbin of history, where it belongs. AG I can't believe (well, I guess I can believe) the number of physicist who think MWI is a valuable contribution to science. If you tell them otherwise they they you that you don't understand physics. Many Worlds is "in the math" (as Sean Carroll claims) so it must be true. They engage in magical thinking, but think they are doing science. Amazing.The many-histories is a logical consequence of the theory. To assume a theory without accepting its consequence is just wrong, or irrational. Bruno Which specific theory formulation are you talking about?Any formulation without physical wave reduction. Everett’s one, for example. With our without the Born rules (the fact that they are derivable or not is not much relevant, as you know I do think that Gleason theorem makes them derivable, but that is not relevant here).There's *quantum measure theory*: Axioms in section 2: https://arxiv.org/pdf/1002.0589.pdfThat is a very interesting paper.But I don't see where Many Worlds as Carroll presents them are necessarily implied by these axioms.They are implied by the SWE, or Dirac. May be the best argument is that the founder have invented the notion of collapse because that is the only way to avoid them.QM predict that I f I put cat in the state dead + alive, and if I look at the cat living/dead state, I will put myself in the state seeing-the-cat-dead + seeing the cat-alive, and without a wave reduction postulate, no branche of that superposition can be made more real or less real than the other.I don’t need quantum mechanics to bet on many-world: like Deutsch I consider that the two slit experiment is enough.I think the alternative is something suggested by Zurek. He shows that decoherence plus einselection will make the reduced density matrix strictly diagonal, i.e. he solves the preferred basis and derivation of the Born rule.OK.Then he suggests, but doesn't really argue, that the universe cannot have enough information to realize all the non-zero states on the diagonal and so only a few can be realized and that realization is per the Born rule. This is what Carroll would dismiss as a "disappearing world interpretation”;Me too.but it would provide a physical principle for why worlds disappear, i.e. branches of lowest probability are continually pruned.The problem is that they are lowest only in special circumstances, and if I prepare the a photon in the relevant state normalised by sqrt(2), like sending it on a sem-tranparent mirror, both “worlds” have high probabilities (1/2). Only the “aberrant” worlds disappears, it seems to me.
When I wrote "lowest" I was assuming the context of MWI...not a single universe. The Bekenstein bound implies that the Hubble volume has an upper bound for information capacity of it's surface area in Planck units. This number is around 2.4e106. So as I read Zurek, he thinks this provides a kind of probability cutoff and branches less probable than 0.4e-106 have zero probability. And, more to the point, in the limit of large N, where N is the number of degrees of freedom in the environment the off diagonal terms of the reduced density matrix go to zero; but this cutoff makes them exactly zero for N>2.41e106. I haven't figured out many branchings it would take to reach this number, but with some 1e98 particles it wouldn't take very many.
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