Recent content by shadi_s10

Thanks for your explanations. Is using general relativity in order to get to the pressure inside a star OK? I am doing some calculations and so far I think the gravitational potential would be quit different.

Dear friends, Does anyone know how we can solve the TOV equations for a non constant density? In all the references, I just saw the solution for a constant density. Thanks in advance for the help :)

You are right. I have read the book before but I got lost between all the equations. Sometimes, asking and discussing, things get more clear. Thanks again!

I think I found it! In the paper that you mentioned above, they say the location of the first peak is given by \begin{equation} l_a \approx \pi \frac{d_A(z_r)}{r_s(a_r)}\end{equation} where \begin{equation} d_A = R/\sqrt{\Omega_m}\end{equation} So this way the shift parameter would change the...

Thanks for the explanations. However, I still don't get the 1.7 number! I agree that it somehow shows some kind of distance, however, if you see " L. Amendola and S. Tsujikawa. Dark Energy: Theory and Observations", they claim that the shift parameter is about 1.7. What I want to know is ...

sure, sorry for the last one! \begin{equation} R = \sqrt{\frac{\Omega^0_m}{\Omega^0_k}}sinh(\sqrt{\Omega^0_k}\int^{z_{dec}}_{0}{\frac{dz}{E(z)}}) \end{equation}

Dealing with CMB, people sometimes refer to the shift parameter; R = \sqrt{\frac{\Omega^0_m}{\Omega^0_k}}sinh(\sqrt{\Omega^0_k}\int^{z_{dec}}_{0}{\frac{dz}{E(z)}}) I know that it is related to the position of the first acoustic peak, however, the amount is around 1.7. What does this mean?! does...

Sorry friends! I found the problem! I have changed one of the directory's name! :smile:

Hi again! any suggestions for my last problem? since I installed the grii package, "read " command does not work any more :(

Dear friends, Now that I am using GRTensor, I get t a very strange error- at least for me! I used to read an .mpl file, consisting some functions, definitions, ... but now maple cannot read my file. I mean when I say: read "/home/.../ myfile.mpl", I get to the error: Error, unable to read...

Hi everyone! How can I make a Riemann tensor for a metric in a locally inertial frame? What I mean is that, maple makes Riemann tensor by Riemann(ginv, D2, Cf1), and it uses the four sentences consisting Christoffel symbols and their derivatives in order to make the Riemann tensor. However, I...

It is interesting to mention that there are actually two different R in this equation. The first one on the left hand side is R(g) and the second one in the right hand side is R(T)

Yes this is the exact equation. But I do not know how they reach to this by combining \nabla_{\lambda} ( \sqrt{-g} G g^{\mu\nu})=0 and F R_{\mu\nu} - \frac{1}{2} f g_{\mu\nu} = \kappa ^{2} T _{\mu\nu} !

Hi friends, going through Palatini gravity, I cannot do the variation for palatini f(R) gravity and get to the famous equation (Tsujikawa dark energy book equation 9.6): R_{\mu\nu}-\frac{1}{2} g_{\mu\nu} = \frac{\kappa^{2} T_{\mu\nu}}{F} - \frac{F R -f}{2F} g_{\mu\nu} + \frac{1}{F}...

Thanks!