Recent content by Saeide

Well I found how to prove it; That was so simpler than what I really thought! By the way I'm so thankful for your attention Tom. I will go for the Poincare algebra as the next step!

Dear all, Poincare transformation construct a group, better to say noncompact Lie group. I want to prove this fact but I don't know how...; I mean the general characteristics- associativity, closure, identity element and inversion element. I would appreciate it if anyone could help me or...

Using weak-field Kerr, I want to check the result I've got by linearized GR. That's why I'm interested in Kerr. So I could describe Earth's spacetime by weak-field Kerr, while quadrupole moment could also be obtained by superposition in linearized GR, don't I?

Yes you're right; when I talk about GR, the higher moments would obviously be involved. But the question that I have in my mind is that, while we describe a general metric -without any specific characteristic considered for- with linearized GR, therefore we can conclude that the slow-rotation...

So it means that we could not consider the quadruple for earth? Maybe it's better to ask it in this way; While we obtain a linearized GR for a weak-field limit, for a general metric g ab, and we use it for Earth case too, could we deduce that weak-field Kerr, which is just one specific metric...

Hi all, I want to know if slow-rotation weak-field limit of Kerr metric is also acceptable for the Earth situation or not. It has been shown that in this limit, Kerr metric is reduced to Schwarzschild metric plus a cross term that indicates rotation. So thanks in advance, Saeide

Yes you're right. I forgot about the flat space limit.

Hi all, Papapetrou line element describes an axial symmetric stationary spacetimes and the coordinates that appear in this metric are just similar to cylindrical coordinates; I mean they are labeled ρ, z and phi. I want to know if they are really the cylindrical coordinate or not; In other...

The inertial frame where the light exists and the light's frame are the same, while the light velocity is constant and as a result we can say that the frame is inertial. Of course our physics laws are applicable only for velocities less than c, just like singularities in GR that we are not aware...

When you look at an someone moving with the velocity near to that of light, in your rest frame, you see that he gets older more slowly than if he was in your inertial frame, and obviously it doesn't mean that he is younger in his inertial frame too. The fact is that you are talking about the...

So thanks, that was so helpful. I wonder how I didn't get it so far!

Hello, We know that NUT spacetime is just like a massless rotating black hole, that this consideration introduces a new concept "magnetic mass", and I know just a little about its metric form and the parameters appear in it. While I was searching for NUT spacetime and its metric, I mostly...