Hello and sorry for the obvious question but: on this forum when the OP writes "Relevant equations", should we assume that it is given in the problem too or that the OP believes that these are the equations that should be used? Because in this specific case, they constitute an additional...
Thank you, this is what I was looking for because I was trying to see how a delta function could be introduced here. However, is it always correct in general? If the dependence of A was not a plane-wave or a simple analytical function of r, could we still use this trick? It could happen that the...
Hello everyone,
I was looking at the light matter interaction Hamiltonian and I worked out a simple calculation where I was surprised to see that I had to introduce an explicitly non-local vector potential if I want to go further:
$$\langle\psi|...
Thank you both for your answers. I already have the book by Altland and Simmons called Condensed Matter Field Theory, so I assume it is the one you refer to. I only need to find the chapter now! And the Nobel review looks great to start learning about the topic.
For interested people I have...
Hello,
I was not sure whether this should belong to this section or the condensed matter section. I am wondering if after about 15 years in research in topological condensed matter, there exist well-recognized references for beginners in the topic. Books or courses but also review articles...
I think they are right, it is even written in the title of the thread. What I am trying to do is to give a solution that could help the OP understand better how it works by providing a derivation that is closer to what they were trying to achieve.
Sometimes, it is helpful to see a correction of...
What I mean above is that the message quoted below is directly leading to the correct answer if explicited correctly. We simply do not need all the sine and cosine, we replace them with x/r, y/r and z/r.
Hello,
I don't know if the author will see this answer but I would like to point out that I do not find their idea to use spherical coordinates to calculate ##\nabla f## nonsensical.
Indeed, from the expression of the gradient operator in spherical coordinates...
Sorry I tried to stay general as I was thinking it would be easier for people to answer but I guess it makes everything confusing.
I am thinking about nanostructures where you have a part of the wave function which is a Bloch state (like in regular solid state physics) and a second part which...
Thank you for your answer. When you use group theory and couple this discrete angular momentum with the spin projection, ##L_{z}(180^{\circ})+S_{z}##, is there a way to define the eigenstates of the Hamiltonian? I am used to couple L+S for L=1 and S=1/2 in semiconductor physics to obtain J=3/2...
Hello,
I was wondering if it was possible to define good quantum numbers in solid state physics or chemistry when systems posses a discrete cylindrical symmetry Cnv. I know that in terms of angular momentum, L and L_z will be good quantum numbers for spherical symmetry, then only L_z is a good...
Thank you for your answers. If I understand correctly, the second method is to use the already established formulas such as the ones given here:
https://en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics)#Second-order_and_higher-order_corrections
e.g.:
$$E_{n}(\epsilon) =...
Hello,
I am looking for a reference which describe perturbation theory with two parameters instead of one. So far, I did not find anything on the topic. It might have a specific name and I am using the wrong keywords. Any help is appreciated.
To be clear, I mean I have ##H =...