Freeze-in Dark Matter Perturbations are Adiabatic

TL;DR

This paper demonstrates that dark matter perturbations produced via the freeze-in mechanism are purely adiabatic, aligning with current observational constraints on isocurvature modes.

Contribution

It establishes that freeze-in dark matter naturally results in adiabatic perturbations, resolving potential conflicts with observational bounds.

Findings

Dark matter perturbations from freeze-in are purely adiabatic.

Freeze-in mechanism is consistent with isocurvature constraints.

Supports viability of freeze-in as a dark matter production process.

Abstract

We show that the large-scale perturbations in the dark matter generated by the freeze-in mechanism are only of adiabatic nature. The freeze-in mechanism is not at odds with the current stringent constraints on isocurvature perturbations.