Dark Matter from freeze-in and its inhomogeneities

TL;DR

This paper explores how dark matter produced via freeze-in processes inherits standard model inhomogeneities, ensuring compliance with cosmological iso-curvature perturbation constraints.

Contribution

It demonstrates that freeze-in dark matter naturally inherits adiabatic inhomogeneities, addressing a key aspect of structure formation and cosmological consistency.

Findings

Dark matter inherits adiabatic inhomogeneities from the Standard Model.

Freeze-in processes satisfy bounds on iso-curvature perturbations.

Re-thermalization of the Standard Model fluid occurs during freeze-in.

Abstract

We consider generic freeze-in processes for generation of Dark Matter, together with the consequent re-thermalization of the Standard Model fluid. We find that Dark Matter inherits the Standard Model adiabatic inhomogeneities on the cosmological scales probed by current observations, that were super-horizon during freeze-in. Thereby, freeze-in satisfies the bounds on iso-curvature perturbations.