Dark Matter with Density-Dependent Interactions

TL;DR

This paper explores a model where dark matter interactions depend on a scalar field that varies with density, affecting annihilation rates and detection prospects across cosmic history.

Contribution

It introduces a density-dependent interaction model for dark matter, linking cosmological evolution with local detection signals, and analyzes observational constraints.

Findings

Annihilation cross section can increase by a factor of 10^6 from freeze-out to today.

Models can achieve scattering cross sections near astrophysical bounds.

Density-dependent interactions can reconcile early universe and current detection data.

Abstract

The decay and annihilation cross sections of dark matter particles may depend on the value of a chameleonic scalar field that both evolves cosmologically and takes different values depending on the local matter density. This possibility introduces a separation between the physics relevant for freeze-out and that responsible for dynamics and detection in the late universe. We investigate how such dark sector interactions might be implemented in a particle physics Lagrangian and consider how current and upcoming observations and experiments bound such dark matter candidates. A specific simple model allows for an increase in the annihilation cross section by a factor of $10^6$ between freeze-out and today, while more complicated models should also allow for scattering cross sections near the astrophysical bounds.