On Saturday, October 26, 2019 at 2:26:48 PM UTC-6, Philip Thrift wrote: > > > > On Saturday, October 26, 2019 at 3:15:15 PM UTC-5, Alan Grayson 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 >>> >>> >>> @philipthrift >>> >> >> Sorry, I really don't get it. For me "interference" refers to waves which >> cross each other and add their amplitudes, positively and negatively. 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 >> >> > > The point is you don't need to have waves (or the wave function) in the > first place. > > You get the same results (interference, entanglement) with or without the > waves or wave function. > > @philipthrift >
Why not make your point with waves so at least it's intelligible? You can get the same results in the Heisenberg Picture, but to understand "interference" you need to at least start with waves. 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/2a2e56a0-4bd5-40df-93e0-309f108452ab%40googlegroups.com.
