Recent content by phypar

I have a result for the differential cross section d\sigma/d\eta dP_T^2, but I want to obtain the corresponding differential yields dN/d\eta dP_T^2. How to relate yields to cross section?

This is exactly what i don't understand, so in the transposition there is a change of the postion of the fermions fields, but according to the anti-commutation rule of them, shouldn't there be a minus sign? I know there is something wrong in my understanding, but just cannot figure it out.

In the standard QFT textbook, the Hermitian conjugate of a Dirac field bilinear \bar\psi_1\gamma^\mu \psi_2 is \bar\psi_2\gamma^\mu \psi_1. Here is the question, why there is not an extra minus sign coming from the anti-symmetry of fermion fields?

Thanks. I just found the solution from another paper. So first one should perform the integration to polar coordinates using the formula: \int_0^\pi d\theta \cos(n\theta)/( 1+a\cos(\theta))=\left(\pi/\sqrt{1-a^2}\right)\left((\sqrt{1-a^2}-1)/ a\right)^n,~~~a^2<1,~~n\geq0 then perform the...

I confront an integration with the following form: \int d^2{\vec q} \exp(-a \vec{q}^{2}) \frac{\vec{k}^{2}-\vec{k}\cdot \vec{q}}{((\vec q-\vec k)^{2})(\vec{q}^{2}+b)} where a and b are some constants, \vec{q} = (q_1, q_2) and \vec{k} = (k_1, k_2) are two-components vectors. In the...

thank you for give the reference, is Eq.(3.5) the equation for the scalar perturbation?

What is the "equation for the amplitude of scalar perturbations"? I am studying inflation now, and in a book I read "equation for the amplitude of scalar perturbations", in the paper the author does not explain what is it, could anyone give some detail on this equation or any reference? Thanks...

I know the trace tr[\gamma_5 a\!\!\!/b\!\!\!/c\!\!\!/d\!\!\!/] in 4-dimensional space-time, how is the result of it in D dimension? Is it the same as in 4 dimension?

Thanks a lot, you gave a very clear explanation. Now I understand it fully.

In the textbook, usually the fermion mass renormalization is introduced as follows: the mass shift \delta m must vanish when m_0=0. The mass shift must therefore be proportional to m_0. By dimensional analysis, it can only depend logarithmically on \Lambda (the ultraviolet cutoff): \delta m \sim...

Thanks for all the replies. I found the mistake in my calculation. \chi_1 and \chi_2 are Grassman variables, thus satisfy the anti-commutation relation, which means \chi_1\chi_2-\chi_2\chi_1 \neq 0

The Majorana mass term is expressed from a single Weyl spinor. But I am a little confused by the expression. For example, see Eq. (2) in http://arxiv.org/pdf/hep-ph/0410370v2.pdf \mathcal{L}=\frac{1}{2}m(\chi^T\epsilon \chi+h.c.) Here \chi is the Weyl spinor and \epsilon = i\sigma^2 is...