Cosmological constraints on dark matter models with velocity-dependent annihilation cross section

TL;DR

This paper derives cosmological constraints on dark matter models with velocity-dependent annihilation cross sections, focusing on how early universe observations limit models with enhanced annihilation rates at low velocities.

Contribution

It provides the first comprehensive analysis of cosmological constraints on velocity-dependent dark matter annihilation models, especially those with Sommerfeld or Breit-Wigner enhancements.

Findings

Big-bang nucleosynthesis constraints are significant.

Cosmic microwave background observations impose strict limits.

Velocity-dependent models are tightly constrained by cosmological data.

Abstract

We derive cosmological constraints on the annihilation cross section of dark matter with velocity-dependent structure, motivated by annihilating dark matter models through Sommerfeld or Breit-Wigner enhancement mechanisms. In models with annihilation cross section increasing with decreasing dark matter velocity, big-bang nucleosynthesis and cosmic microwave background give stringent constraints.