On Tue, Dec 05, 2017 at 12:18:02PM +1100, Bruce Kellett wrote: > On 5/12/2017 11:53 am, Russell Standish wrote: > > On Tue, Dec 05, 2017 at 11:26:53AM +1100, Bruce Kellett wrote: > > > On 5/12/2017 3:15 am, Bruno Marchal wrote: > > > > I think that is enough to get the macroscopic superposition, as, like I > > > > explained, you have to take into account not just the quantum > > > > indeterminacy, + the classical chaos. You might need to shake for some > > > > minutes. > > > You could shake for longer than the age of the universe and you will still > > > not convert quantum uncertainties and classical thermal motions into a > > > macroscopic superposition. Do you know nothing about coherence? And the > > > fact > > > that coherent phases between the components are what separates a > > > superposition from a mixture? Random quantum uncertainties and thermal > > > motions are not coherent, so cannot form superpositions. > > > > > To repeat - coherence and superposition are orthogonal concepts. A > > fully decohered multiverse is still in a superposition. > > But that superposition is only of the whole multiverse, and we do not have > access to that. The concepts are not orthogonal, because any finite physical > system will not, in general, be in a superposition of any kind. The > distinction between pure states -- coherent superpositions -- and mixed > states is fairly fundamental if you want to make any progress in fundamental > physics.
Of course. My point is simply that a mixed state is still a superposition, just not a coherent one. It may just be a pernicketty language thing, but I do see a lot of disagreements on this list just because people are using language in different ways. > > > Re the length of time for quantum uncertainty to affect macroscopic > > state, much less than the age of the universe is required. > > The Poincaré recurrence time for the general decohered state is certainly of > the order of the age of the universe. Quantum uncertainties can affect the > macroscopic state in some circumstances -- particular when there is a clear > route for amplification of the quantum effects, as in most quantum > experiments. It has been suggested that the chaotic rotation of Saturn's > moon Hyperion is related to quantum effects, but that is a particularly > unstable system. > The Poincare recurrence time is usually much longer than the mixing time of a chaotic system. I'm not sure what the relevance is to what we're talking about. > > Whilst the StosszahlAnsatz will be strictly speaking incorrect, as I > > understand it it is very approximately true. This will entail that quantum > > randomness will affect classical randomness on about the same > > timescale as the mean free time of molecules in a gas at room > > temperature, or about 0.1 ns. > > I think this remains to be proved for the general case. > > > Unless you are proposing some other source of randomness that is not > > quantum? Then I'm all ears. Classical physics doesn't have it, it is > > deterministic. > > Randomness in the sense that I am using it arises in deterministic systems > from lack of knowledge of the initial conditions. As in the coin toss, in > general you do not know the initial conditions with sufficient accuracy to > predict the outcome with certainty. What other type of randomness is > relevant in classical situations? Thermal motions are sufficiently random > FAPP. And thermal motions are amplified from more minor uncertainties in the molecular scattering process, which are quantum in nature ISTM. If lack of knowledge in initial conditions were all there is, then the state of the coin (or dice) is completely determined by the initial conditions (just unknown), in which case they're not exactly a random device, just (possibly) pseudorandom. In such a case, there will not be two universes, one with heads and one with tails, just one universe with one or the other outcome. -- ---------------------------------------------------------------------------- Dr Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Senior Research Fellow hpco...@hpcoders.com.au Economics, Kingston University http://www.hpcoders.com.au ---------------------------------------------------------------------------- -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
