Recent content by wphysics

Could you tell me in more detail? In fact, I could not find any integral representations of Hankel functions that matches with my integration.

I am working on Schwartz QFT book problem 14.3, particularly part (c). Basically, it asks us to evaluate the following integration. \int \cfrac{d^3 p}{2\pi^3} \omega_p e^{i \vec{p} \cdot (\vec{x}-\vec{y})} where \omega_p = \sqrt{p^2 + m^2} I could perform the angular integration, and the...

Yes. That explanation is the most common one. Let me put it in this way. For spin 0 particle, supersymmetric transformation transforms it to spin 1/2 particle. If we do again, it should be back to spin 0 and effectively, its effect is translation. I cannot draw this picture in my head physically.

Yes! I am wondering why it is the case conceptually.

In Super Poincare algebra, we know that the anti commutator of two weyl spinors is proportional to translation. This is the equivalence that I am talking. Thanks

Hello, I have one conceptual question. I have been working on Supersymmetry. Now, I understand that twice of supersymmetric transformation is equivalent to translation mathematically(naively). However, I don't quite understand why this should be the case conceptually. Supersymmetric...

I am now at home, so I don't have Weinberg right now. I will post the relevant equations as soon as I am back to the school. Thank you for your interest. QUOTE=rigetFrog;4772632]I don't have Weinberg. Put up the equations.

Hello, I am reading the book, The Quantum Theory of Fields II by Weinberg. In page 426 of this book (about soliton, domain wall stuffs), we have Eq(23.1.5) as the solution that minimizes Eq(23.1.3). The paragraph below Eq(23.1.5), the author said "The advantage of the derivation based on...

Currently, I am working on Thermal Quantum Field Theory. In the introduction to that, many authors point out that infinitely many degrees of freedom and infinite volume are special. In one reference that I am reading said "The famous equivalence between the Heisenberg and the Schro ̈dinger...

I think the measure must not be invariant. If so, ##i \Gamma [ \phi_0 ] ## is independent of ##\phi_0##, and Weinberg mentioned about this point. I have already read Srednicki book, but for me, that is not enough. Thank you for your answer

Thank you for your answer, but I don't see why your answer is relevant my question and don't understand either. In previous paragraph in Weinberg book, for general field ##\phi^r (x)##, ##i \Gamma[\phi(x)]## must be the sum of all one-particle-irreducible connected graphs with arbitrary numbers...

I am working on Quantum Effective Action in Weinberg QFT vol2 (page 67). In the last paragraph of page 67, the author said "Equivalently, ## i \Gamma [ \phi _0 ] ## for some fixed field ... with a shifted action ##I [ \phi + \phi_0 ]## : i \Gamma [ \phi _0 ] = ∫_{1PI, CONNECTED} ∏_{r,x}...

In CDM case, I think it can be treated as a scalar density perturbation only. What I asked was that the form of equation describing dark matter perturbation is really the form of hydrodynamics form?

I think our point is getting close. First of all, thank you so much for your willingness to answer my silly question. I have further question. As you said, if the free electron density is high enough, we can think that electrons and photons are in thermal equilibrium. Than, does it mean that...

I appreciate for your answer But what I am asking is not expanding equations, but the legitimacy for using hydrodynamical description. In which physical circumstances, can we use this description? Weinberg said in case of photons, the high density of free electron is, which is I don't know why.