I recently came across a new user who has asked several questions on the site but has not accepted any. Probably he is not aware of this feature. Is it okay if I inform him about it?
i.stack.imgur.com/PcJid.png I feel certain someone has asked this question before. If so, does anyone know where to find the answer? If not, I will post that question, but it's a bit vague so if anyone has suggestions to improve it please let me know :)
In an Adiabatic Free expansion, the entropy increases, but in an Adiabatic Slow and Reversible Expansion, the entropy doesn't increase, why? What is the intuitive explanation for this phenomenon? What happens at the molecular level that the entropy increases in the first case but doesn't in the second?
@DevanshMittal Temperature is constant in the free expansion, so the volume determines the entropy. In the reversible case temperature changes. I am not sure what you mean by molecular level, entropy is not really a molecular property, but rather a property of the phase space
I would like to ask a question about function quantities, but I didn't find any adequate tags. If I didn't miss something, it might be useful to introduce a new tag, for example "physical quantities".
@Archer I'm not quite sure that you mean by "citations generated online" but most sites intended to provide citation offer BibTeX or similar formats to copy-paste.
Possible silly question, but if we perform a transformation on a system in which first we apply the active version, and then we apply the passive version, do we expect to end up with the original pre-transformation system again, or the system with the transformation "applied twice" to it?
In other words are the active and passive transformation identical, or are they in some sense "inverses" of eachother
I don't know why I get tripped up on this so much, but based on what I've been attempting, applying the passive followed by the active (or vise versa) should land us back at the original, untransformed system
if you think this really matters, I'd ask what problem you're trying to solve - in what situation do you have to first "apply the active version" then "apply the passive version"?
I'm afraid I don't really know what an "online magazine" is, nor why there would be a specifically indigenous magazine on physics or where you referred to it.
I have no idea if that's what you want because you haven't really managed to formulate a coherent English sentence about what you want. "can you refer some link" is not how 'refer' works as a word, and I still don't know what the 'indigenous' and 'telegram' business was all about.
@ACuriousMind Thanks for the link, sorry for using the word "indigenous" it is clearly out of the track. second about telegram all I was saying is I get some inputs from my friends using a group on this platform
@ACuriousMind Sorry didn't see this, I agree the wording is a bit loaded if that's what you're saying. It just bugged me because even if it is bad wording it still has to make sense somehow :P I drew some pictures and I was right the first time
So in more precise language we would refer to (on manifolds) active transformations as diffeomorphisms $F:M\rightarrow N$ and passive transformations as linear maps between all tangent spaces, which I suppose essentially is a map between tangent bundles $J:TM\rightarrow TN$
where $J$ is the Jacobian
Or rather, each individual map $J:T_pM\rightarrow T_{F(p)}N$ is a Jacobian, idk if there's name for the entire map
It's getting a bit elaborate now, but I think I get it
For correlation functions in QFT, when we have just two field operators (ie. $\langle0|\hat\phi(x)\hat\phi(y)|0\langle$ this is the propagator, but what is the purpose/interpretation of correlation functions with more than two field operators?
if I had to guess based on what I know about that, it looks like the amplitude for a field to spontaneously produce $n$ particles at the points $x,y,...$ and then for those particles to disappear, so we start and end in the vacuum state
but it will turn out to be closely related to the probability of $k$ of those particles to scatter into the other $n-k$ particles
If you just learned about the propagator, you can't really see that. Wait for whatever you're reading to derive the LSZ formula and scattering amplitudes
Srednicki chapter 5 does LSZ in an easier way than Peskin, the jist is here, you can see the correlation functions arising as a by-product in working out $<f|i>$