Parametric-Resonance Production of QCD Axions

Abstract

Dark matter axion production can be significantly enhanced through a generic cosmological mechanism: primordial temperature fluctuations periodically modulate the axion mass during the QCD phase transition, thereby triggering parametric resonance in axion field evolution. This interplay between the resonance and the misalignment mechanism moves the predicted axion mass window for the observed dark matter abundance to $10^{-4}-10^{-3}\text{eV}$, shifting the preferred mass to previously unexplored higher ranges.

Comments: 5+2 pages, 3 figures