Axion Bose-Einstein Condensation: a model beyond Cold Dark Matter

TL;DR

This paper explores how axion Bose-Einstein condensates differ from traditional cold dark matter in structure formation, highlighting their unique effects on halo rotation and cosmic microwave background anisotropies.

Contribution

It introduces a model where axion BEC influences dark matter dynamics beyond standard cold dark matter, especially in non-linear regimes.

Findings

Axion BEC can produce net rotation in dark matter halos.

It can cause alignment of cosmic microwave anisotropy multipoles.

Differences between axion BEC and CDM are significant in non-linear evolution.

Abstract

Cold dark matter axions form a Bose-Einstein condensate if the axions thermalize. Recently, it was found that they do thermalize when the photon temperature reaches T ~ 100 eV(f/10^12GeV)^1/2 and that they continue to do so thereafter. We discuss the differences between axion BEC and CDM in the linear regime and the non-linear regime of evolution of density perturbations. We find that axion BEC provides a mechanism for the production of net overall rotation in dark matter halos, and for the alignment of cosmic microwave anisotropy multi-poles.