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