Recent content by conana

Thank you for your response, DeathbyGreen. Despite the authors claiming to have used the stationary phase approximation, I don't believe it applies as the cosine (or complex exponential) does not possesses a stationary phase. This is why I believe one should develop an asymptotic series with...

I was hoping to get some assistance in reproducing a calculation from https://arxiv.org/abs/0803.1292 (https://journals.aps.org/pra/abstract/10.1103/PhysRevA.78.012304 for the published version). A certain four-spin correlation function for Kitaev's spin-1/2 model on the honeycomb lattice is...

This classic: https://www.amazon.com/dp/0748402535/?tag=pfamazon01-20

I cannot say if this is true in general (and I expect it is not), but here in Cologne (and in Bonn, as well) the language of instruction at the graduate level (for physics) is English. Furthermore, the graduate school pays for its international students to take German language courses if they so...

In quantum mechanics, both of those objects are operators. The operator \mathbf{r} operates on state vectors in real space, whereas the operator \sigma operates on spinors in spin space. You can treat (symbolically) the dot product between \mathbf{r} and \sigma as a normal dot product between...

(a) interaction between two systems whose individual Hilbert spaces are H_A and H_B can be describe by states |\psi\rangle belonging to the direct product of these Hilbert spaces H=H_A\otimes H_B. (b) an entangled state |\psi\rangle_C belongs to this direct product Hilbert space, however, it...

I can only recommend that you relax. That is something you will not have time to do for the next several years if you want to seriously pursue physics.

Thank you vanhees71 for your response. I believe I understand the main idea of what you are saying and will do some playing around with this idea.

Oh wow... I was originally trying to do just that except that I was thinking I would use the residue theorem... which makes no sense for this problem. Wow that is easy. Thanks, The_Duck. However, I am still curious as to where my overly-complicated solution goes wrong. Any thoughts?

While preparing for an exam I came across an integral of the form \int_0^\infty dx\;e^{-\alpha x}\sin{q x} with q,\alpha>0. My question will be regarding my solution to the integral which I present as follows: I expand the sine function as a Taylor series and differentiate with respect to...

In position representation (one dimension), the momentum operator \hat{P}\rightarrow-i\hbar\dfrac{d}{dx}. You want to square this. Squaring a derivative operator just turns it into a second derivative. The process is then taking \langle\hat{P}^2\rangle=\langle\Psi_1|\hat{P}^2|\Psi_1\rangle...

Thank you for the reply. Between your advice and me talking to another professor I think I have straightened everything out. I was confusing summing eigenvalues and operators and also some of the labeling conventions. Feeling pretty good, but my exam is in an hour so it's back to the books for...

Homework Statement Two spin-1/2 particles are governed by \dfrac{J^2}{2I}+\omega_0 J_z where J=J_1+J_2. At time t = 0 the total angular momentum is measured and found to be 0. (a) At time t, J_{1z} is measured. What are the possible results and what is the probability of each? Homework...

Homework Statement Use epsilon-delta proof to show that \lim_{z\to z_0}(z^2+c)=z_0^2+c. Homework Equations \forall\epsilon>0 \exists\delta>0 \forall z (|z-z_0|<\delta\Rightarrow|f(z)-\omega_0|<\epsilon) The Attempt at a Solution So f(z)=z^2+c and \omega_0=z_0^2+c. In order to write my...

Rereading my initial post, the problem is not quite as clear without the diagram (however, I have no means of scanning the diagram). The x and y axes both lie within the plane of the table and after the collision the mass km is moving ONLY in the y direction. I also neglected to mention that my...