Dark Matter in a Bi-Metric Universe

We study the possibility to describe dark matter in a model of the universe with two-scale factors and a nonstandard Poisson bracket structure characterized by the deformation parameter κ. The dark matter evolution is analyzed in the early stages of the universe, and its relic density is obtained via the Freeze-In and Freeze-Out mechanism. We show that by fixing κ and the initial ratio of energy densities present in the different sectors of the universe, the space of thermal average annihilation cross-sections and dark matter masses compatible with the standard cosmology prior to Big Bang Nucleosynthesis (BBN), is enlarged. This feature of the model is compatible with nonstandard cosmology. © 2023 World Scientific Publishing Company.