Recent content by Ravendark

Homework Statement I would like to compute the following integral: I = \int\limits_0^\pi \mathrm{d}\theta \, \frac{\sin^2 \theta}{a^2 + b^2 - 2 \sqrt{ab} \cos \theta} where ##a,b \in \mathbb{R}_+##. 2. The attempt at a solution Substitution ##x = \cos \theta## yields I = \int\limits_{-1}^1...

Homework Statement Consider the fermionic part of the QCD Lagrangian: $$\mathcal{L} = \bar\psi (\mathrm{i} {\not{\!\partial}} - m) \psi \; ,$$ where I used a matrix notation to supress all the colour indices (i.e., ##\psi## is understood to be a three-component vector in colour space whilst...

Mhh, it seems you're right... Now I'm a bit confused...about which RHS/LHS are you talking about? You mean consistent on which argument ##\partial_\mu## actually acts?

Thank you very much, I got it...I totally forgot, that there exists an identity for the derivative of the delta function: ##\partial_\mu \delta^{(4)}(y-x)=-\partial_\mu \delta^{(4)}(x-y)##.

Right...instead of transfer the derivative to ##\bar\psi## I can perform the derivative directly since I know how the derivative w.r.t. ##\bar\psi## looks like. But why is it "forbidden" to use partial integration ((11) to (12) in my first post) at this point (apart from the fact that this...

Homework Statement [/B] Consider the following action: $$\begin{align}S = \int \mathrm{d}^4 z \; \bar\psi_i(z) \, (\mathrm{i} {\not{\!\partial}} - m)_{ij} \, \psi_j(z)\end{align}$$ where ##\psi_i## is a Dirac spinor with Dirac index ##i## (summation convention for repeated indices). Now I would...