Cosmological Inhomogeneities with Bose-Einstein Condensate Dark Matter

TL;DR

This paper investigates how Bose-Einstein condensate dark matter affects the growth of cosmological inhomogeneities, revealing faster increases in key cosmological parameters compared to standard pressureless dark matter models.

Contribution

It provides analytical expressions for perturbation growth in BEC dark matter within Newtonian and relativistic frameworks, highlighting differences from standard cosmology.

Findings

Faster growth of scale factor, gravitational potential, and density contrast with BEC dark matter.

Analytical expressions derived for small pressure limit.

Comparison with standard cosmology shows significant differences.

Abstract

We consider the growth of cosmological perturbations to the energy density of dark matter during matter domination when dark matter is a scalar field that has undergone Bose-Einstein condensation. We study these inhomogeneities within the framework of both Newtonian gravity, where the calculation and results are more transparent, and General Relativity. The direction we take is to derive analytical expressions, which can be obtained in the small pressure limit. Throughout we compare our results to those of the standard cosmology, where dark matter is assumed pressureless, using our analytical expressions to showcase precise differences. We find, compared to the standard cosmology, that Bose-Einstein condensate dark matter leads to a scale factor, gravitational potential and density contrast that increase at faster rates.