Recent content by Ken Gallock

I was thinking about the theoretical upper limit. So, you mean that even a very long wavelength, such as an infinitely long one, can be detected in principle?

Yes, that is what I meant. Sorry. For example, we can use a device like a laser; The wavelength of the light can be changed as we turn a dial of the device. By doing so, the wavelength of the light can be changed (I assume nothing affects the wavelength while the light propagates). Could you...

Thanks for your reply. So, I think I should know about more basic concepts. Let me ask the following: The situation is that there is a light source in flat spacetime which emits a light of wavelength ##\lambda##. And an observer, who detects the light, is in the same frame of reference of the...

I am looking for some resources describing the following content: A light with wavelength ##\lambda## is propagating in flat spacetime. The light redshifts as its wavelength gets larger and larger. In quantum field theory, this causes an infrared divergence of the field. What I want to know...

(finally, I figured out the password of PF...) Thank you for your reply. It is very helpful.

Hi. I was wondering what is the relationship between Gaussian normal coordinates and Riemann normal coordinates. Thanks.

Hi. I have a question about covariance matrices (CMs) and a standard form. In Ref. [Inseparability Criterion for Continuous Variable Systems], it is mentioned that CMs ##M## for two-mode Gaussian states can be symplectic transformed to the standard form ##M_s##: ## M= \left[ \begin{array}{cc}...

Sorry for my late reply. Somehow I didn't get the notification. :( Your reply helped me a lot. I did calculation as follows: \begin{align} &\langle f|: \psi^\dagger(x_1)\psi(x_1)\psi^\dagger(x_2)\psi(x_2) :|i\rangle \notag \\ &=\langle f| \psi^\dagger(x_1)\psi^\dagger(x_2)\psi(x_1)\psi(x_2)...

Hi. My question is about nucleon-nucleon scattering. In David Tong's lecture note, he discusses Wick's theorem and nucleon scattering (page 58-60). My problem is that I don't know how to calculate the second line of eq(3.48): \begin{equation} <p'_1, p'_2|:\psi^\dagger (x_1) \psi (x_1)...

Thanks. I will do my best.

I think I should have noted the motivation of this problem. We want to think about a generalization of 4D Clifford algebra. For example, in ##1+3## dimension, we can set ##\Gamma##s as \begin{align} \Gamma^{0\pm}:=\dfrac12 (\gamma^0 \pm \gamma^1),\\ \Gamma^{1\pm}:=\dfrac12 (i\gamma^2 \pm...

Homework Statement Consider gamma matrices ##\gamma^0, \gamma^1, \gamma^2, \gamma^3## in 4-dimension. These gamma matrices satisfy the anti-commutation relation $$ \{ \gamma^\mu , \gamma^\nu \}=2\eta^{\mu \nu}.~~~(\eta^{\mu\nu}=diag(+1,-1,-1,-1)) $$ Define ##\Gamma^{0\pm}, \Gamma^{1\pm}## as...

Thanks! I got the same result!

Is it different when I'm dealing with spinor fields?

I want eq(1.53): $$ \delta \mathcal{L}=-\omega^\mu_{~\nu}x^\nu\partial_\mu \mathcal{L}. $$