> On 26 Oct 2019, at 22:15, Alan Grayson <[email protected]> wrote: > > > > On Thursday, October 24, 2019 at 4:53:00 PM UTC-6, Philip Thrift wrote: > On Thursday, October 24, 2019 at 5:07:34 PM UTC-5, Alan Grayson wrote: > On Thursday, October 24, 2019 at 12:56:29 PM UTC-6, Philip Thrift wrote: > On Thursday, October 24, 2019 at 9:27:14 AM UTC-5, Alan Grayson wrote: > On Monday, October 21, 2019 at 6:21:26 PM UTC-6, Alan Grayson wrote: > On Monday, October 21, 2019 at 12:03:20 AM UTC-6, Brent wrote: > > On 10/20/2019 10:46 PM, Alan Grayson wrote: >> On Sunday, October 20, 2019 at 6:35:10 PM UTC-6, Brent wrote: >> >> On 10/20/2019 4:58 PM, Alan Grayson wrote: >>> On Sunday, October 20, 2019 at 11:35:13 AM UTC-6, Brent wrote: >>> >>> On 10/19/2019 6:56 PM, Alan Grayson wrote: >>>> Sean says the decoherence time is 10^(-20) sec. So when the box is closed, >>>> the cat is in a superposition of alive and dead during that time interval, >>>> assuming the decay hasn't happened. If that's the case, I don't see how >>>> decoherence solves the paradox, unless we can assume an initial condition >>>> where the probability of one component of the superposition, that the cat >>>> is dead, is zero. Maybe this is the solution. What do you think? AG >>>> >>>> Maybe this is an easier question; after decoherence, assuming the >>>> radioactive source hasn't decayed, what is the wf of the cat? Is the cat >>>> in a mixed state, alive or dead with some probabIlity for each? AG >>> >>> You can't "assume the radioactive source hasn't decayed". The point >>> Schroedinger's thought experiment is that when the box is closed you don't >>> know whether or not it has decayed and so it is in a superposition of >>> decayed and not-decayed and the cat is correlated with these states, so it >>> is also in a superposition of dead and alive. >>> >>> Brent >>> >>> I thought you might say this. OK, then what function does decoherence have >>> in possibly solving the apparent paradox of a cat alive and dead >>> simultaneously. TIA, AG >> >> It doesn't necessarily solve "that problem". Rather it shows why you can >> never detect such a state, assuming you buy Zurek's idea of envariance. One >> way to look at it is it's the answer to Heisenberg's question: Where is the >> cut between the quantum and the classical? Once envriance has acted, then >> the result is classical, i.e. you can ignore the other possibilities and >> renormalize the wave function. >> >> Brent >> >> Woudn't you agree that if the system, in the case a cat, goes classical >> after 10^(-20) sec, its state must be a mixture at that point in time even >> if the box hasn't been opened? AG > > In MWI it's only a mixture FAPP. But if you haven't opened the box (and > Schroedinger was assuming an ideal box) you don't know whether the cat has > "gone classical" or not. So your representation of its state is still a > superposition. That's the QBist interpretation. The wf is just what you > know about the system. > > Please remind me; if the wf is a superposition before the box is opened, what > exactly does this mean? That is, what does interference mean in this > circumstance? TIA, AG > > Please indulge me on this. At this point I have no clue what superposition > and/or interference means in this context. TIA, AG > > > All these are couched in the vocabulary of the formulation and interpretation > of the theory one begins with, and so they have ambiguous meanings. > > @philipthrift > > Can you answer the question assuming the CI? AG > > > > Just translate this into "CI", in whatever terms you like. It gives the same > answers, so what difference does it make? > > The probability P for an event to occur is given by the square of the complex > magnitude of a quantum amplitude for the event, Q. The quantum amplitude Q > associated with an event is the sum of the amplitudes associated with every > history leading to the event. > > [This] specifies how probabilities are to be computed. This item builds the > concept of superposition, and thus the possibility of quantum interference, > directly into the formulation. Specifying that the probability for an event > is given as the magnitude-squared of a sum made from complex numbers, allows > for negative, positive and intermediate interference effects. This part of > the formulation thus builds the description of experiments such as the > two-slit experiment directly into the formulation. A history is a sequence of > fundamental processes leading to the the event in question. > > http://muchomas.lassp.cornell.edu/8.04/Lecs/lec_FeynmanDiagrams/node3.html > <http://muchomas.lassp.cornell.edu/8.04/Lecs/lec_FeynmanDiagrams/node3.html> > > @philipthrift > > Sorry, I really don't get it.
Nobody does, really. Even if the mechanist know the why, the how will still delude us for long. Like many said; to understand QM is to understand that there is a big metaphysical problem there. > For me "interference" refers to waves which cross each other and add their > amplitudes, positively and negatively. OK. > Why, if we give a probability interpretation to the amplitudes, does this > have anything to do with interference, particularly for a wf for S's cat > which is entangled with the wf of a radioactive source? AG Because if we send just one particle, we can predict some place where we will with certainty not find the particle, so that we have to take into account the wave “associated” to one single particle. Now, EPR Bell, but already Einstein at the Solvay congress in 1927, explains why a mechanical/physical association of the particles with the wave (like with hidden variable) will not do, without adding FTL actions, or introducing super-determinism, or killing Realism in Physics. Yes, wave interfere and that is the problem when the wave seems to describe either our own knowledge/ignorance, or a single particles. There are less problem, and perhaps no serious problem at all, when we accept that the physicists obeys to the wave formalism too, in which case we get coherent set of histories, like Mechanism predicted. In that case we can understand that the laws of physics originates in the statistics on all relative computations. Bruno > > > -- > 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/c3418bf6-58f5-41a6-862f-8f5337c9115f%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/c3418bf6-58f5-41a6-862f-8f5337c9115f%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/9A25C9F7-3276-44F4-9551-D4BB4F28A80E%40ulb.ac.be.
