If you still want to know: The MSc at imperial consists of three blocks, namely compulsory modules, optional modules and dissertation. The compulsory modules are (the last time I checked) QFT, QED, Unification and Particle Symmetries (and oh boy are you going to have fun with this one :) )...
Hi all,
I'm hoping somebody can save me from this impending frustration induced aneurysm. The problem lies with Maple's physics package and is this:
I am in an FLRW spacetime with metric
##ds^{2}=dt^{2}−a(t)^{2}(\frac{dr^{2}}{1−kr^{2}}+r^{2}d\theta^{2}+r^{2}sin^{2}(\theta)d\phi^{2})##
and...
Hi all,
I am trying to out what happens when a gravitational wave caused by a monochromatic, electromagnetic plane wave interacts with a charged particle. As we all know, the electromagnetic wave causes the particle to follow a figure of eight shaped path (in the particles rest frame anyway)...
Put like that it does make sense. Now I look at it, the action used in various papers does have the Ricci tensor squared in one form or another. Suppose I really should have noticed :biggrin:.
Thanks for the quick reply
Hi all.
I keep coming across the term "quadratic gravity" in various GR papers and don't entirely understand the concept as it doesn't seem to be explained anywhere. It seems to appear most frequently in the context of pp-waves. So I was hoping somebody could enlighten me as to what its all...
This is the terminology I have been taught, but it might have other names elsewhere. The Ricci 1-form is the contraction of the curvature form (or Ricci 2-form):
R_{a}=i_{b}R^{b}_{ a}
(Using R twice might not be the best convention) where R^{b}_{ a} is given by Cartan's second structure...
I know what you mean, calculating the Christoffel symbols by hand can be an absolute nightmare. But given all the different conventions and notations, a list would be confusing to the point being useless for most people.
However, if you are trying to do it for it for a commonly used metrics...
Hi all,
once again I'm stuck on something I am quite certain is silly, but here it goes. My confusion pertains to the equation
Ric=R^{a}\otimes e_{a}
where Ric is the Ricci tensor, R^{a} is the Ricci 1-form and e_{a} are the elements of an orthonormal basis.
Now, let's say for...
Ok, if I'm going to describe the full problem this should go in the cosmology section.
The goal is to rewrite the Klein-Gordon equation in terms of a perturbation to the scalar field. So, starting from
\frac{d^{2}\phi}{dt^{2}} + 3H\frac{d\phi}{dt} + \frac{dV}{d\phi}=0
where...
Sorry, just some old habits. What I mean is this: A function f(x) is perturbed by δx so f(x+δx). What is the differential of this:
\frac{d}{dx}f(x+\delta x)
which is what I think it should actually look like.
Hi all,
I'm a bit stuck on what should probably be fairly simple, but I'm looking for a general way to do
\partial_{x}f(x+\delta x)
Any help would much appreciated.