Inflatable Dark Matter

TL;DR

The paper introduces 'Inflatable Dark Matter', a scenario where late-time inflation reduces dark matter density, resolving overproduction issues in many models without fine-tuning or anthropic reasoning.

Contribution

It proposes a novel late-time inflation mechanism that adjusts dark matter abundance, accommodating various candidates and scales without fine-tuning.

Findings

Late-time inflation can dilute dark matter density effectively.

This scenario allows heavy or light thermal relics to be viable.

Non-thermal axion abundances can be brought to acceptable levels.

Abstract

We describe a general scenario, dubbed "Inflatable Dark Matter", in which the density of dark matter particles can be reduced through a short period of late-time inflation in the early universe. The overproduction of dark matter that is predicted within many otherwise well-motivated models of new physics can be elegantly remedied within this context, without the need to tune underlying parameters or to appeal to anthropic considerations. Thermal relics that would otherwise be disfavored can easily be accommodated within this class of scenarios, including dark matter candidates that are very heavy or very light. Furthermore, the non-thermal abundance of GUT or Planck scale axions can be brought to acceptable levels, without invoking anthropic tuning of initial conditions. A period of late-time inflation could have occurred over a wide range of scales from ~ MeV to the weak scale or above, and could have been triggered by physics within a hidden sector, with small but not necessarily negligible couplings to the Standard Model.