Do Baryons Trace Dark Matter in the Early Universe?
Abstract
Baryondensity perturbations of large amplitude may exist if they are compensated by darkmatter perturbations such that the total density is unchanged. Primordial abundances and galaxy clusters allow these compensated isocurvature perturbations (CIPs) to have amplitudes as large as ∼10%. CIPs will modulate the power spectrum of cosmic microwave background (CMB) fluctuations—those due to the usual adiabatic perturbations—as a function of position on the sky. This leads to correlations between different sphericalharmonic coefficients of the temperature and/or polarization maps, and induces polarization B modes. Here, the magnitude of these effects is calculated and techniques to measure them are introduced. While a CIP of this amplitude can be probed on large scales with existing data, forthcoming CMB experiments should improve the sensitivity to CIPs by at least an order of magnitude.
 Publication:

Physical Review Letters
 Pub Date:
 December 2011
 DOI:
 10.1103/PhysRevLett.107.261301
 arXiv:
 arXiv:1107.1716
 Bibcode:
 2011PhRvL.107z1301G
 Keywords:

 98.80.Es;
 98.65.Dx;
 98.70.Vc;
 Observational cosmology;
 Superclusters;
 largescale structure of the Universe;
 Background radiations;
 Astrophysics  Cosmology and Extragalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 4 pages, 3 figures, updated with version published in Phys. Rev. Lett. Results unchanged. Added expanded discussion of how to disentangle compensated isocurvature perturbations from weak lensing of the CMB. Expanded discussion of early universe motivation for compensated isocurvature perturbations