Recent content by Bruno Cardin

So, I have a hamiltonian for screening effect, written like: $$ H=\sum_{k}^{}\epsilon_{k}c_{k}^{\dagger}c_{k}+ \frac{1}{\Omega}\sum_{k,q}^{}V(q,t)c_{k+q}^{\dagger}c_{k} $$ And I have to find an equation for the time evolution of the expected value of the operator ##c_{k-Q}^{\dagger}c_{k}##. I...

Actually, the first guy was right (look at the first reply). It is a heat-like force. ##(\rho \U^{\mu})_{;\mu}=0,## is not neccesarely true, if there is a change in the internal energy of the fluid (not mass creation, but internal energy, so that ##\rho=\rho_{0} + \epsilon## . Look again at...

This is how I get that equation, in GR with covariant derivatives (but it's the same in Minkowski space-time): We have charged dust, so the system is described by the energy-momentum tensor: $$ T^{\alpha \beta} = \rho U^{\alpha} U^{\beta} + E^{\alpha \beta} $$ With E being the e.m...

Thanks for the reply. What I mean with "extra term" is that when you have a free particle (let's say a test particle of mass m) in the presence of an e.m field that generates a tensor E, then the equation of motion for said particle is ## m a= F## where a is it's four acceleration and F is the...

Thanks for the reply. I kind of understand better now, but there's still something bugging me. So, basically, I'm working with charged dust, which is described by energy-momentum tensor: $$ T^{\alpha \beta}= \rho U^{\alpha} U^{\beta} + E^{\alpha \beta}$$ where U is the four velocity, ##\rho##...

Hello. Could anyone help me with some insight in an extra term appearing in the motion equations of a relativistic fluid? I say extra term, because it's not present on the motion for a test particle, as it follows: Let's propose Minkowski space-time, the motion equations for a fluid with zero...