On the Validity of Bounds on Light Axions for $f\lesssim10^{13}$ GeV

TL;DR

This paper investigates the non-perturbative behavior of light axion-like particles near massive bodies for decay constants below 10^{13} GeV, highlighting implications for experimental detection.

Contribution

It demonstrates that quadratic interactions cause non-perturbative axion field values for certain parameter ranges and generalizes this to axion-like particles.

Findings

Non-perturbative axion field values occur for f  10^{13} GeV and m_a  710^{8}/f eV^2.

Experimental observables are affected by the non-perturbative effects.

The results extend to axion-like particles beyond QCD axions.

Abstract

Light bosonic dark matter fields that can be treated like a classical wave have non-linear field values close to massive bodies. Here we make the important observation that the quadratic interactions of axion dark matter lead to non-perturbative axion field values for values of the decay constant of $f\lesssim 10^{13}$ GeV and masses $m_a\lesssim 7\times10^{8}/f\ {\rm eV^2}$ and generalise this result for axion-like particles. We identify experimental observables impacted by this effect.