Speaker
Description
We study the evolution of axion cold dark matter overdensities in low-temperature reheating cosmologies, focusing on the interplay between the temperature-dependent axion mass and the radiation background. We show that modes entering the horizon prior to both reheating and the onset of oscillations experience a significant enhancement driven by their coupling to radiation perturbations. This enhancement is maximized when the temperature at which the axion mass becomes constant, $T_\Lambda$, lies slightly above the reheating temperature, allowing for efficient growth while avoiding the suppression effects of curvature and radiation perturbations near reheating. We discuss the implications for the formation of small-scale structure such as axion miniclusters.