Do we need extra radiation?

A theory of extra radiation in the Universe

Kazunori Nakayamaa, Fuminobu Takahashib and Tsutomu T. Yanagidab


Abstract
Recent cosmological observations, such as the measurement of the primordial
4He abundance, CMB, and large scale structure, give preference to the existence of extra radiation component. The extra radiation may be accounted for
by particles which were in thermal equilibrium and decoupled before the big bangnucleosynthesis. Broadly speaking, there are two possibilities: 1) there are about 10 particles which have very weak couplings to the standard model particles and decoupled much before the QCD phase transition; 2) there is one or a few light particles with a reasonably strong coupling to the plasma and it decouples after the QCD phase transition.

Are we back to square one with dark matter?

From here (http://arxiv.org/abs/1010.4290):

General relativistic effects on non-linear matter power spectrum

Authors calculated the matter power spectrum based on next to the linear order perturbation theory (3rd order perturbation theory, 3PT) fully taking GR effect into account.
Basically, P_{3PT}=P_L+P_{22}+P_{13}, where non linear contributions cancel each other at large scale (P_{22}+P_{13}~0, or linear Pk is good enough), but boost up the Pk at small scale ( P_{22}+P_{13}>0).
P_{3PT} has been calculated for decades using Newtonian approximation, but this work is the first result to include genuine GR effect. As naively expected, correction due to GR is negligible, and the use of Newtonian approximation is verified.
arXiv:1010.3489

Falling into Virgo

The preferred direction of infalling satellite galaxies in the Local Group

Authors: Noam I Libeskind, Alexander Knebe, Yehuda Hoffman, Stefan Gottloeber, Gustavo Yepes, Matthias Steinmetz

http://arxiv.org/abs/1010.1531

"It becomes apparent from this figure, that as the MW and M31 travel towards virgo they scoop up subhalos in their path. These subhalos reside in a filamentary like structure that also points in the direction of Virgo."

Dark Matter Halo Density Profile

From arXiv:0810.1522

Title: The Diversity and Similarity of Simulated Cold Dark Matter Halos

From arXiv:1010.2539

Title: The Origin of Dark Matter Halo Profiles

Constraining the expansion rate of the Universe using low-redshift ellipticals as cosmic chronometers arXiv:1010.0831v1

Authors used a spectral feature around 4000A of Early Type Galaxies (ETG) to measure the Hubble constant. The result, H_0 = 72.3 \pm 2.8 (68% confidence), is in a good agreement to that of WMAP, and the error (systematic dominated?) is comparable to the one from SNIa.
Since the method is a direct measurement of the age of galaxies, it will be very useful for cross checking the values of w(z) etc... measured from other types of future DE missions.

Constraints on the Dark Matter Particle Mass from the Number of MilkyWay Satellites

http://arxiv.org/abs/1004.1459

Interesting numerical simulation and maybe one explanation to the satellite problem.