Nonperturbative overproduction of axionlike particles via derivative interactions

Abstract

Axionlike particles (ALPs) are quite generic in many scenarios for physics beyond the Standard Model. They are pseudoscalar Nambu-Goldstone bosons that appear once any global U(1) symmetry is broken spontaneously. The ALPs can gain mass from various nonperturbative quantum effects, such as anomalies or instantons. ALPs can couple to the matter sector including a scalar condensate such as inflaton or moduli field via derivative interactions, which are suppressed by the axion decay constant, fχ. 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 fχ/ΦI1, where ΦI denotes the initial amplitude of the coherent oscillations of the scalar condensate, φ. We will briefly mention how such dangerous overproduction would affect dark matter and dark radiation abundances in the Universe.