Recent content by KDPhysics

It seems like I overlooked the simple fact that the state cannot change during a sudden, ##\textit{finite}## perturbation, so I was right in assuming that the spin would be ##|+\rangle## at ##t=0^+##. To understand why the system's state must be continuous over the sudden perturbation in the...

Consider an uncharged particle with spin one-half moving with speed ##v## in a region with magnetic field ##\textbf{B}=B\textbf{e}_z##. In a certain length ##L## of the particle's path, there is an additional, weak magnetic field ##\textbf{B}_\perp=B_\perp \textbf{e}_x##. Assuming the electron...

One last question, the Unruh modes as defined in Sean Carroll's "Spacetime and Geometry" are: $$h_k^{(1)} = \frac{1}{\sqrt{2\sinh(\pi \omega/a)}}\big(e^{\pi \omega/2a} g_k^{(1)} + e^{-\pi \omega/2a} g_{-k}^{(2)}{}^*\big)$$ On the other hand this paper gives a different definition: $$h_k^{(1)} =...

I see, thanks!

But couldn't the left moving negative frequency modes be analytic in that half of the complex plane?

In Carroll "Spacetime and Geometry" I found the following explanation for why the analytically extended rindler modes share the same vacuum state as the Minkowski vacuum state: I can't quite understand why the fact that the extended modes [\tex]h_k^{(1),(2)}[\tex] are analytic and bounded on...

Thanks for the answers, very enlightening!

In p.385 of Griffiths QM the vector potential ##\textbf{A} = \frac{\Phi}{2\pi r}\hat{\phi}## is chosen for the region outside a long solenoid. However, couldn't we also have chosen a vector potential that is a multiple of this, namely ##\textbf{A} = \alpha \frac{\Phi}{2\pi r} \hat{\phi}## where...

Thanks, very clear explanation!

So the so-called act of measurement in the OP is the painting process, not the blind man somehow "measuring" the colour of the apple? This seems to make a lot more sense now.

Thank you. Suppose then that instead of colouring apples i consider randomly assigning a spin to an electron (here surely quantum effects are coherent). If I don't observe the spin of the electron, then does this mean that the electron is in a definite spin state, but I just haven't performed a...

Thank you. So this case would fall under "incomplete information situations" rather than superpositions as you have described?

I guess my question is what makes something capable of being in a superposition, and other things not?

just because an apple isn't an elementary particle doesn't mean that it can't be in a superposition right?

But couldn't you apply that logic to an electron's spin as well? It's either spin up or spin down.