Recent content by nicf

Yes, I think I understood this part already; this motivation makes sense to me and I agree with it. I realize now that my last post was too long and not very clear, so I'll try to say it with fewer words :). It is commonly argued that the measurement problem can't be solved with ordinary...

Excellent! I think this gets at the heart of what I was asking about. Specifically, I think I was failing to appreciate both (a) the obvious-once-you've-stated-it fact that mixed terms like ##\psi_1\psi_2^*\otimes\rho^E## prevent us from deducing the ##\frac{1}{\sqrt{2}}(\psi_1+\psi_2)## result...

This part I actually think I understand well enough to explain. The q-probability distribution isn't the same object as the q-expectation; it's a measure on ##\mathbb{R}##, whereas the q-expectation is just a number. (In fact, the q-expectation is the mean of the q-probability distribution.) You...

I might be misunderstanding you, but I actually think (b) is not what @A. Neumaier is saying, at least if by "random nonlinear fluctuations" you mean that there's some change to the unitary dynamics underlying quantum mechanics. Rather, he's saying that the nonlinearity comes from...

Exactly, that's why I'm confused! My impression is that @A. Neumaier is somehow denying this, and that somehow the refusal to describe macroscopic objects with state vectors is related to the way he gets around this linearity argument, although I don't see how. If we're supposed to be positing...

This is a clearer way of saying exactly what I meant, thank you :). Let me use this as a jumping-off point to try to state my original question more clearly, since I think I am still confused. The part of the measurement problem that's relevant to my question is exactly the part that...

Thanks for taking the time to reply! I have a couple more questions, but what you've said so far is helpful. Yes, that's what I meant --- I'm referring to the variable that encodes which of the two readings ends up being displayed on the detector, and this omits the vast majority of the...

I'm a mathematician with a longstanding interest in physics, and I've recently been enjoying reading and thinking about Arnold Neumaier's thermal interpretation, including some threads on this forum. There's something that's still confusing me, though, and I'm hoping someone here can clear it...

This would be lovely. I have books that seem to imply that we can no longer assign a particle interpretation to the states when we're working with an interacting theory. Is this just, as Chopin said, because the states are no longer eigenstates of the Hamiltonian? Or is there something more...

There's an analogous affront to our naiveté when we go from (nonrelativistic) classical to quantum mechanics, though, and it's one we can completely resolve: the question "where is the electron?" in, say, the double-slit experiment doesn't have a well-defined answer, but the electron does have a...

Might as well keep using the same numbers. (1) By the state space I mean the Hilbert space where the states live. In, say, spin-0 single-particle quantum mechanics this is (once you pick a basis) just the space of all the wavefunctions. This doesn't depend on the Hamiltonian. The eigenstates of...

I'm a grad student in math, and I've been trying to learn some physics on the side by taking some classes and reading books. I took a class on quantum field theory last semester that was taught out of Srednicki; the class was very good, but I found myself at the end with a conceptual question...