Reheating-Induced Axion Dark Matter After Low Scale Inflation

TL;DR

This paper introduces a new cosmological scenario where axion dark matter is produced during reheating after low-scale inflation through kinetic mixing with the inflaton, expanding potential models for axion dark matter.

Contribution

It presents the 'inflaxion' framework, analyzing axion dynamics during reheating and proposing a novel mechanism for axion dark matter production at low inflation scales.

Findings

Axion can be produced even with inflationary Hubble scale below its mass.

Reheating dynamics can lead to axion abundance matching observed dark matter levels.

Implications for QCD axion and axion-like particles are discussed.

Abstract

A kinetic mixing between the axion and the inflaton allows for a production of axion dark matter even if the inflationary Hubble scale is smaller than the zero-temperature axion mass. We analyze the axion dynamics in this recently discovered "inflaxion" framework, and present a new cosmological scenario where the axion drifts away from its vacuum during the reheating epoch, giving rise to the observed dark matter abundance. We discuss the implications for both the QCD axion and axion-like particles.