# Recent content by S.P.P

Thanks :)
2. ### WMAP Cl data

I'd like to compare some models of mine against results from WMAP. Is there anywhere I can get the data, l(l+1) Cl / 2pi as a function of l? I see plenty of images of the TT, TE power spectra with error bars on them from WMAP, but can't seem to find the data. Ideally I'd like to plot my models...
3. ### De Broglie problem

Are you sure that 8 should not be a 4?
4. ### How do I split equations in LaTeX

Thank you, that has sorted it out. :smile:
5. ### How do I split equations in LaTeX

Couldn't think of a better place to post this. I'm writing a document in latex that has several very large equations in it. I can split them up so that they take up two or three lines using the \begin{split} command or \begin{align} command, but If I need to split a line that is contained within...
6. ### Rasing and lowering indicies

Brilliant, thanks very much! :smile:
7. ### Rasing and lowering indicies

In GR the metric can raise or lower indices, but which index will it raise in this case: \delta^{ij} \partial_i \xi_j is it, \partial^j \xi_j or, \partial_i \xi^i Or are these equal?
8. ### Covariant derivative

just a quick query, I know that, \nabla_0 A_{\alpha}= \partial_0 A_{\alpha} - \Gamma^{\beta}_{0 \alpha} A_{\beta} But what does \nabla^0 A_{\alpha} equal?
9. ### Help computing Christoffel coefficient

aha! got it. \Gamma^i_{0j} = \frac{a'}{a}\delta^{ij}+\frac{1}{2}g^{i\nu}\partial_0(h_{\nu j}) . If I expand the last term out, \frac{1}{2}(\eta^{i\nu}-h^{i\nu})\partial_0(h_{\nu j}) . Ignore higher order terms (ie h^2), using the metric signiture (+,-,-,-) coupled with the fact that only...
10. ### Help computing Christoffel coefficient

there should be a prime on h, that was a typo on my part.
11. ### Help computing Christoffel coefficient

I'm starting to think that the answer I've been given has a typo, and should read \delta^i_j instead of \delta_{ij} . I've lost the dummy indices as I've summed over v . When v=0 everything equalled zero, so the next index was j (where j = 1,2,3). Is this not the way to proceed? Also, I...
12. ### Help computing Christoffel coefficient

That's a bit closer than I can get. Does \delta^i_j = \delta_{ij}?
13. ### Doppler Effect and sound

I see, of course :)
14. ### Doppler Effect and sound

Yes I believe thats right.
15. ### Help computing Christoffel coefficient

Not so much a homework problem, more needing help understanding where something comes from. I've attached a jpg file with what I need help on. I've done a general relativity course at uni but can't seem to work out what should be a very simple problem.