arXiv: 3 May 2010

Large angle anomalies in the CMB
Authors: Craig J. Copi (CWRU), Dragan Huterer (Michigan), Dominik J. Schwarz (Bielefeld), Glenn D. Starkman (CWRU)
http://arxiv.org/abs/1004.5602v1
We review the recently found large-scale anomalies in the maps of temperature anisotropies in the cosmic microwave background. These include alignments of the largest modes of CMB anisotropy with each other and with geometry and direction of motion of the Solar System, and the unusually low power at these largest scales. We discuss these findings in relation to expectation from standard inflationary cosmology, their statistical significance, the tools to study them, and the various attempts to explain them.


Dark energy with non-adiabatic sound speed: initial conditions and detectability
Authors: Guillermo Ballesteros, Julien Lesgourgues
http://arxiv.org/abs/1004.5509v1
Assuming that the universe contains a dark energy fluid with a constant linear equation of state and a constant sound speed, we study the prospects of detecting dark energy perturbations using CMB data from Planck, cross-correlated with galaxy distribution maps from a survey like LSST. We update previous analytical estimates by carrying a full Bayesian analysis of mock data. We find that it will only be possible to exclude values of the sound speed very close to zero, while Planck data alone is not powerful enough for achieving any detection, even with lensing extraction. We also discuss the issue of initial conditions for dark energy perturbations in the radiation and matter epochs, generalizing the usual adiabatic conditions to include the sound speed effect. However, for most purposes, the existence of attractor solutions renders the perturbation evolution nearly independent of these initial conditions.

Impact of Dark Matter Microhalos on Signatures for Direct and Indirect Detection
Authors: Aurel Schneider (1), Lawrence M. Krauss (2), Ben Moore (1) ((1) University of Zurich, (2) Arizona State University)
Detecting dark matter as it streams through detectors on Earth relies on know-ledge of its phase space density on a scale comparable to the size of our solar system. Numerical simulations predict that our Galactic halo contains an enormous hierarchy of substructures, streams and caustics, the remnants of the merging hierarchy \cite{Moore1999,Sikivie1999} that began with tiny Earth mass microhalos \cite{Bergstrom1999,Berezinsky2003,Diemand2005}. If these bound or coherent structures persist until the present time, they could dramatically alter signatures for the detection of weakly interacting elementary particle dark matter (WIMP). Using numerical simulations that follow the coarse grained tidal disruption within the Galactic potential and fine grained heating from stellar encounters, we find that microhalos, streams and caustics have a negligible likelihood of impacting direct detection signatures implying that dark matter constraints derived using simple smooth halo models are relatively robust. We also find that many dense central cusps survive, yielding a small enhancement in the signal for indirect detection experiments.