Non-perturbative over-production of axion-like-particles (ALPs) via derivative interaction

TL;DR

This paper investigates how axion-like particles (ALPs) can be non-perturbatively overproduced through derivative interactions with scalar condensates, potentially impacting dark matter and dark radiation in the universe.

Contribution

It introduces a scenario where ALPs are abundantly produced via derivative couplings, leading to possible overclosure of the universe, a novel insight into ALP cosmology.

Findings

ALPs can be overproduced if $f_\chi/\Phi_{\rm I} \ll 1$.

Overproduction can affect dark matter and dark radiation.

The study highlights conditions for ALP overabundance in the early universe.

Abstract

Axion like particles (ALPs) are quite generic in many scenarios for physics beyond the Standard Model, they are pseudoscalar Nambu-Goldstone bosons, and appear once any global $U(1)$ symmetry is broken spontaneously. The ALPs can gain mass from various non-perturbative quantum effects, such as anomalies or instantons. ALPs can couple to the matter sector incluidng a scalar condensate such as inflaton or moduli field via derivative interactions, which are suppressed by the axion {\it decay constant}, $f_\chi$ . Although weakly interacting, the ALPs can be produced abundantly from the coherent oscillations of a homogeneous condensate. In this paper we will study such a scenario where the ALPs can be produced abundantly, and in some cases can even overclose the Universe via odd and even dimensional operators, as long as $f_\chi/\Phi_{\rm I} \ll 1$, where $\Phi_{\rm I}$ denotes the initial amplitude of the coherent oscillations of the scalar condensate, $\phi$. We will briefly mention how such dangerous overproduction would affect dark matter and dark radiation abundances in the Universe.