Recent content by Sonderval

Thanks. But is this ##\delta I[h]## the same as ##\delta I[h]/\delta h##? In analogy to functions, I would expect the first to be the equivalent of a total differential (in functional logic a variation) and the second to be equivalent to a derivative. I find the nomenclature quite confusing, to...

I understand a functional to be a map from a space of functions to a number, as in my example above: $$ F[f] = \int_a^b f^n(x) dx$$ A Functional gets a function as input and gives a number. The functional derivative should (if I understand things correctly, which I probably don't) produce a new...

I am confused whether the functional derivative ($\delta F[f]/\delta f$) is itself a functional or whether it is only a function The Wikipedia article is not very rigorous https://en.wikipedia.org/wiki/Functional_derivative but from the examples (like Thomas-Fermi density), it seems as if the...

Thanks. I was 99% sure that this would be the case since any interference terms would contain products like ##\langle idler 1 | idler 2\rangle##, but it is good to have this confirmed.

Consider the following experiment: A photon hits a beam splitter, then a non-linear crystal (nichtlinearer Kristall - sorry, prepared the image in German) on each path that does parametric down conversion, splitting the photon into a signal and an idler. The idlers proceed to two detectors (D1...

@vanhees71 I'm not sure I understand. The beam splitters do not change polarization here, polarization comes into it only in situation 3 and 4 where I explicitly added the filters. That is why i simply added the appropriate H and V to the states in the 3rd equation. I totally agree that there is...

@vanhees71 I now tried to calculate things explicitly and believe my idea above to be incorrect. (Calculation follows below, I'd be very grateful for someone to check it.) However, I do see a problem with causality if my idea were correct: Image we set up the light source to send one photon per...

@charters Yupp, that's worrying me as well.

I have a question on how exactly polarizing filters would influence interference in a Mach-Zehnder interferometer. To explain, I'll show some configurations and what I would expect to happen - please tell me if I am incorrect anywhere. Here is the standard MZI configuration with no filters and...

@vanhees71 Thanks. I was just confused because my sources never mentioned that there would be alternative ways of doing it - some used the asymmetric beam splitters, some used symmetric ones, but none mentioned that both exist.

@Aidyan and Cthugha Funnily, the references you both provided on first sight again seemed to contradict each other - Zetie talking about 180° phase shift on reflection, Cthugha explaining that the shift is 90° But thanks to the reference by Henault, I finally understand it: There are symmetric...

I'm confused by the phase shifts in a Mach-Zehnder interferometer because I keep finding two different explanations. One explanation (for example, given on Wikipedia, but also elsewhere) states that on each reflection, the phase shift is 180 degrees, but only, if light is reflected from the...

@PeterDonis Thanks a lot. I assume the same is true for the case of the expanding hole. I find this somewhat surprising - the black hole expands and the photon moves "outwards" - but that's probably simply a consequence of using global coordinates. OTOH, it shows that Penrose diagrams are...

Dear all, I have a question on Penrose diagrams. Consider a collapsing star that forms a black hole with a Schwarzschild radius normalized to 1. What happens in the Penrose diagram when additional matter falls in? I suspect the diagram then has to look like this : When the outer shell (second...

@atyy Thanks. Yes, I suspect you're right and that this is what is more or less implied by the qualifier "local OPF", but at least to me it is not very clearly stated.