A mechanism for formation of Bose-Einstein condensation in cosmology

Abstract

We introduce a toy model of scalar particles with a trilinear scalar coupling in cosmology. The trilinear coupling ${\varphi }^2\chi$ causes production of non-relativistic $\varphi$ particles through the process $\chi \chi \to \varphi \varphi$ where, initially, only relativistic $\chi$ particles are present. We consider the initial times of $\chi \chi \to \varphi \varphi$ and observe that the curved space effects promote formation of Bose-Einstein condensate of $\varphi$ particles.

Some technical details in the main text are moved to two appendices. Typos are fixed, and the presentation of the manuscript is improved