Secondary CMB powerspecrum measured SPT

Bow shock

Destruction of solar system by an alien star

A simple planet motion simulation I did for a project in one of the undergraduate course.
I studied what happens to the planets if a solar mass object swing by the Sun closely.

I will explain the details at the journal club meeting.

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."