Recent content by bjaw

Wonderful. I managed to obtain the required relation by extremising the action under X. Thanks so much for the fantastic help you give! Just one more quick question about that link in your last post: can you always equate the conserved quantity relating to (dt/dT) to E/m or is that only for...

It should mean that dO^2 = 0 so that there's no angular component to the worldline. So this gives: ds^2 = -dT^2 + a^2 dX^2 I've also realized that for the second part I can use g(ab)t(a)t(b) = -1 for timelike geodesics, which means that (dt/dT)^2 = 1 + a^2(dX/dT)^2 which gives the second...

I understand what geodesics are and how to calculate them from Christoffel symbols and all that. But I've just come across a question I have no idea about. I've been given the dust filled Friedmann solution: ds^2 = -dt^2 + a(t)^2 (dX^2 + X^2 dO^2) (O=omega) And been told to show that...

Thanks for the swift reponses! That's helped a lot.

Hi everyone, I just have a question regarding a project I'm doing at the moment. I decided to write about the detection of neutrinos, and hence have to explain the Cerenkov effect which is used in the water detectors. What I can't understand is that, from what I've read so far, the Cerenkov...