Recent content by jmlaniel

Thanks Strangerep! I just completely forgot the summation over the indices... That was also enough for me to figure out the rest!

My question concerns the 1/2 factor in the exponential of Eq. (3.49) of Peskin and Schroeder. This equation concerns the Lorentz boost transformation of a spinor along the z-axis (or 3-direction). According to Eq. (3.26): S^{03} = -\frac{i}{2}\begin{bmatrix}\sigma^3 & 0 \\0 &...

Nobody can help me ? :frown:

The angle of incidence is actually quite important since the transmission and reflexion coefficient are function of the incidence angle (I think they are usually called Fresnel coefficient; actually the square modulus are the Fresnel coefficient). Furthermore, the transmitted angle is also...

Can this be done without using the Lorentz gauge (\partial_\mu A^\mu = 0) or is it necessary imposed ?

From what you say, the function f here is : f^\mu = A_\nu \partial^\nu A^\mu I notice that f here is a function of the field (A_\nu) but also function of the derivative of the field (\partial^\nu A^\mu). I have seen that the Lagrangian is not altered when f is a function of the field...

Homework Statement The charge current density operator for the Dirac equation is defined as : s^\mu = - ec \bar{\psi}\gamma^\mu\psi. Homework Equations I need to show that the current density operator commutes when measured at two spacelike separated points : [s^\mu(x),s^\nu(y)] = 0...

Here are some quick answers : 1. Yes, you can do that quite easily with two lasers (since the slits are there only to mimic two point-like light source). However, in order to get them to interfere, they must be coherent (this is not easy to do with two separate laser source since you need...

I am currently reading "Quantum Field Theory" by Mandl & Shaw (2nd edition). In section 2.4, they give an equation for obtaining a conserved quantity (which leave the Lagrangian density invariant) : \frac{\delta f^\alpha}{\delta x^\alpha} = 0 (2.36 in Mandl & Shaw) In other textbooks that...

I have the felling that we got lost somewhere along the way... I might have been misleading in my in two posts. I just want to know if my algebra is correct and that I have to assume that the derivative (normal one and not covariant) of the metric must be zero in order to get the metric...

I agree that my title might be misleading on the fact that my particular term is actually not a tensor by definition. It is actually a part of a larger derivation based on tensor algebra. It is actually related to the lagrangian of the electromagnetic field. I can also confirm that the...

I am trying to proove that the following relation: A_{\nu} \partial_{\mu} \partial^{\nu} A^{\mu} = A_{\nu} \partial^{\mu} \partial^{\nu} A_{\mu} The only way I found is by setting: A_{\nu} \partial_{\mu} \partial^{\nu} A^{\mu} = A_{\nu} \partial_{\mu} \partial^{\nu} g^{\mu \sigma}...

Is there a conclusion on the sign problem on "k"? I just tried to do the integral myself and I found exactly Zee's solution (as shown in post #1) except for the first term (I have the wrong sign on \vec{k}). I don't have the sign problem in the second term. From what I have read in this...

I have to agree with George and Altabeh... I did not see the effect of the new r in the metric factor. My solution is entirely wrong :frown: But thanks a lot for pointing it out! I have tried for the last hour to find a way to fix this and I am unable to do so. I will have to conlude that kev...

I am not sure that I will be able to give a better answer than the one I gave in post #19... It is the way I understand the parameter R. I would welcome a better explanation.