Recent content by Madster

Dear marcus, thank you very much for the nice links, I appreciate. Maybe my question was misleading. The mechanism of the CMB fluctuations is nicely explained but I was more interested in perturbation theory. What is the definition of the linear power spectrum? Is the BAO bump in the...

Dear Experts, I try to understand power spectra for large scale structure and CMB analyses for my exams. I constantly find the expression for linear power spectra P(k) = A\cdot k^{n_s}\cdot T^2(k). I understand that this comes from primodial primodial fluctuations and the tranfer function...

Thanks the last link hosts really good stuff, but can you expain to me why there is also a BAO bump in the dark matter distribution? I mean it should not interact with photons by definition, right?

Thank you very much, another question would be what is observed in the power spectrum. There is imprinted the baryonic acoustic oscillations. What can I imagine this to be? Is it an amplification of fluctuations at a certain scale of approx. 100 Mpc/h ?

Hi. I read some basic cosmology where it is always said that density fluctuations, pertubations can be described in modes of waves. In particular if you use linearised theory where δ(x,t) is Fourier transformed δ(k,t). What exactly is the reason for this? What do the wave modes describe...

Dear all, many people refer to the CMB anisotropy picture by WMAP or Plack and call it acoustic waves. I thought there is the anisotropy of the CMB radiation plotted, what exactly can I imagine to be the acoustic wave of it? Secondly, what exactly is plotted n the famous plot where the...

thanks for the nice answer, so I suppose spacetime curvature is given by the metric and influences the spacetime distance ds. But what are constant time spatial slices? thx

Hi there. I have a dump question for you guys. I really wonder about curvature of spacetime. I read that due to Omega_tot=1 the Universe is assumed to be flat. But on the other hand something like the curvature of the universe is mentioned... I also thought that the energy stress tensor...

And it is used because you can't solve it analytically for more than 2 particles? Or is it just a matter of time?

Hi. I read due interest papers in Arxiv. There is many times refereed to so called N-Body Simulations. Is that for Matter or Dark Matter? How does it work, can someone explain or suggest good readings? THX

thanks, my math is sufficient enough to get the script. So still what mechanism makes the CMB a gaussian random field, or to be more precise, let's us initially approximate the description with a GRF and look for fluctuations?

Dear all, I don't understand why the Cosmic Microwave Background's angular distribution is considered to to a Gaussian random field initially. The rest of the analysis is roughly clear to me, COBE/WMAP/PLANCK measure the CMB Photons and show the temperature fluctuations w.r.t. the mean...

Dear experts, I really wonder how to extract the equation of stats w=\frac P \rho from the Friedmann equations and how one can see that dark energy needs to have w<-\frac13 and why does w<-1 violate the null energy condition. Thanks in advance, madster

the intrinsic mass is invariant under lorentz transformation. the whole dynamic mass discussion is really confusing but practical sometimes

So I use the formula above to get the "proper distant" (comoving) between the observer, us, and the distant object because I integrate from 0, that's again us, to the measured redshift z of the object. OK then but how to get this comoving distance between objects that are at z1=0.1 and z2=0.3 e.g.?