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 @philipthrift -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/36a18a9a-5d17-4b4a-83f6-0319c47c7269%40googlegroups.com.
