> On 13 Sep 2019, at 23:44, Lawrence Crowell <[email protected]> > wrote: > > On Friday, September 13, 2019 at 6:24:11 AM UTC-5, Bruno Marchal wrote: > >> On 13 Sep 2019, at 04:26, Alan Grayson <[email protected] <javascript:>> >> wrote: >> >> >> >> On Thursday, September 12, 2019 at 11:01:54 AM UTC-6, Alan Grayson wrote: >> >> >> On Thursday, September 12, 2019 at 7:45:22 AM UTC-6, Lawrence Crowell wrote: >> On Thursday, September 12, 2019 at 4:20:46 AM UTC-5, Philip Thrift wrote: >> >> >> On Wednesday, September 11, 2019 at 11:45:41 PM UTC-5, Alan Grayson wrote: >> https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/ >> >> <https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/> >> >> >> >> Many Worlds is where people go to escape from one world of >> quantum-stochastic processes. They are like vampires, but instead of running >> away from sunbeams, are running away from probabilities. >> >> @philipthrift >> >> This assessment is not entirely fair. Carroll and Sebens have a paper on how >> supposedly the Born rule can be derived from MWI I have yet to read their >> paper, but given the newsiness of this I might get to it. One advantage that >> MWI does have is that it splits the world as a sort of quantum frame >> dragging that is nonlocal. This nonlocal property might be useful for >> working with quantum gravity, >> >> I worked a proof of a theorem, which may not be complete unfortunately, >> where the two sets of quantum interpretations that are ψ-epistemic and those >> that are ψ-ontological are not decidable. There is no decision procedure >> which can prove QM holds either way. The proof is set with nonlocal hidden >> variables over the projective rays of the state space. In effect there is an >> uncertainty in whether the hidden variables localize extant quantities, say >> with ψ-ontology, or whether this localization is the generation of >> information in a local context from quantum nonlocality that is not extant, >> such as with ψ-epistemology. Quantum interprertations are then auxiliary >> physical axioms or postulates. MWI and within the framework of what Carrol >> and Sebens has done this is a ψ-ontology, and this defines the Born rule. If >> I am right the degree of ψ-epistemontic nature is mixed. So the intriguing >> question we can address is the nature of the Born rule and its tie into the >> auxiliary postulates of quantum interpretations. Can a similar demonstration >> be made for the Born rule within QuBism, which is what might be called the >> dialectic opposite of MWI? >> >> To take MWI as something literal, as opposed to maybe a working system to >> understand QM foundations, is maybe taking things too far. However, it is a >> part of some open questions concerning the fundamentals of QM. If MWI, and >> more generally postulates of quantum interpretations, are connected to the >> Born rule it makes for some interesting things to think about. >> >> LC >> >> If you read the link, it's pretty obvious that Carroll believes the many >> worlds of the MWI, literally exist. AG >> >> Carroll also believes that IF the universe is infinite, then there must >> exist exact copies of universes and ourselves. This is frequently claimed by >> the MWI true believers, but never, AFAICT, proven, or even plausibly argued. > > The idea comes from Tegmark, and I agree with you, it necessitate more than > an infinite universe. It requires also some assumption of homogeneity. > > Of course, (for those who are aware of Gödel 1931 and Turing 1936), > arithmetic contains all computations, which entails, when assuming mechanism, > an infinity of each os us. That explains both where the appearance of > universe come from, and the quantum mechanical type of formalism. In > “many-world”, the “many” makes sense, but the term “world” is not well > defined and should not been taken literally. It is more histories than worlds > per se. > > Bruno > > > > It would be best to separate MWI from the multiverse for at least the moment. > There are several levels of the multiverse. MWI does define a high level > multiverse, but MWI is not all multiverses. > > The first level has to do with what exists beyond the cosmological horizon > and in particular if the spatial surface of spacetime is flat. This would be > an infinite R^3 manifold. Since the level of complexity or the number of > possible states is bounded by the size of the cosmology horizon, out about 13 > billion light years, this means there are other regions that are copies of > this world. This is just plain combinatorics. > > The type II multiverse, or maybe type IIA, is where a deSitter or FLRW > spacetime with an inflationary vacuum at high energy is unstable and there > are vacuum transitions in regions within it. These regions have a vacuum at a > much lower energy and define what are sometimes called pocket worlds. Since > this inflationary cosmology is in a hugely accelerated expansion then these > pockets of vacuum instability are only local. There are some interesting > questions. In particular is the boundary of any such pocket world pinched > off, so to speak, to define a new detached and topologically complete > spacetime? The boundary has quantum field information, and if this > transitions to a spatial surface that is a sphere S^3 or R^3, then this > quantum field information may play some role. > > The next is a type IIB multiverse, which is a multiplicity of these eternally > inflating spacetimes. These may be emergent from entanglement wedges with AdS > spacetimes. > > There is then the type III multiverse, which is the identification of the MWI > as a multiverse. This is where things may get a bit odd. The problem is that > quantum interpretations are physically questionable, or maybe metaphysics, > and this would mean the type III multiverse is really a sort of metaphysics. > The other multiverse scenarios may hold without MWI.
To be franc, I have no interpretation of quantum mechanics (without collapse)which do not imply something akin to the type III multiverse, and when talking about QM, I talk only about this one. It is this type of many-worlds, or better many histories, which confirms the many computations which exists in arithmetic, and whose statistics confirms (up to now) the physical appearance emerging from the many computations (which exists in the same sense that the prime numbers exist (no need to introduce metaphysics here). > > Then there is type IV multiverse that is Max Tegmark's mathematical universe > hypothesis. This is so completely metaphysical that it is hard to take this > as a serious scientific proposition. With mechanism, you can limit the ontology on the natural numbers, and the corresponding metaphysics can make sense of this, in some restricted way. What Tegmark missed is that, with mechanism (which he seems to have adopted) the physical reality becomes a theological reality, which is itself part of the arithmetical truth (with the understanding that the arithmetical truth, although as well definable that the set of real number, is not definable by the machine, nor really by us, and that it is well beyond the computable. Now both human and machine can point on it. Note that eventually we really do not assume more than the natural numbers, and we never assume something like the set of all natural numbers, which we leave at the meta level. So we are back to Pythagorus ontology: only 0, 1, 2, 3, … with the laws of addition and multiplication. The physical reality is then explained by the phenomenological reality the machines are confronted too by internalising their own incompleteness, which Gödel already know the machine are capable of. Physicalism for me is not just quite speculative, it contradicts Mechanism, which is used (explicitly or implicitly) in many domain, like Darwin in biology, or Everett in Quantum Physics. 0 universe, 1 universe, 2 universes, … aleph_0 universes, … aleph_1 universes, etc. are all speculative. But with mechanism, we can prove that there is 0 universe, but one precise set of physical laws emerging from the statistics on all computations seen from inside arithmetic (or Turing equivalent). Bruno > > LC > > > >> What's the argument for such a claim? Morevover, I don't believe a universe >> of finite age, such as ours which everyone more or less agrees began some >> 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not >> some infinite substratum from which it might have arose. AG >> >> -- >> 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] <javascript:>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/everything-list/f85775c7-7914-47e4-83eb-1142b1b58249%40googlegroups.com >> >> <https://groups.google.com/d/msgid/everything-list/f85775c7-7914-47e4-83eb-1142b1b58249%40googlegroups.com?utm_medium=email&utm_source=footer>. > > > -- > 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] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/e8f736e0-cf55-4eaa-93da-145d2073bd73%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/e8f736e0-cf55-4eaa-93da-145d2073bd73%40googlegroups.com?utm_medium=email&utm_source=footer>. -- 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/4D17E876-11EF-4152-829D-C675166C10A7%40ulb.ac.be.
