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? AGYou 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, AGIt 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. BrentWoudn'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.
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