General Freeze-in and Freeze-out

TL;DR

This paper develops a unified CFT-based framework to analyze dark sector production via thermal interactions, extending known formulas to complex processes and providing new insights into Sommerfeld enhancement effects.

Contribution

It introduces a general approach using conformal field theories to study both relativistic and non-relativistic dark sector production, including complex interactions and enhancements.

Findings

Reproduces known $2\to n$ process formulas

Extends to general $m\to n$ processes and interacting dark sectors

Derives Sommerfeld enhancement from unitarity fermion theory

Abstract

We use the framework of relativistic and non-relativistic conformal field theories (CFT) to derive general results relevant for the production of weakly coupled and strongly coupled dark sectors through thermal interactions. Our result reproduce trivially known formulas for $2\to n $ processes and extend to general $m\to n$ processes as well as interacting dark sectors. As concrete examples we consider freeze-in of a relativistic CFT coupled to the SM with contact interactions and derive Sommerfeld enhancement of non-relativistic cross-sections from the theory of fermions at unitarity.