Altered axion abundance from a dynamical Peccei-Quinn scale

We build a model in which the relic abundance of axions is altered from the standard misalignment mechanism, either increased or decreased, due to the presence of a new light scalar that couples to the radial part of the Peccei-Quinn (PQ) field. The light scalar makes the effective PQ symmetry-breaking scale dynamical, altering the early-time dynamics for the axion and affecting its late-time dark matter abundance. We analyze this new mechanism semianalytically and numerically, showing that we can accommodate both lighter or heavier axion dark matter, compared to the standard treatments. We discuss implications of the model for axion searches and fundamental physics.

Automated summary

We propose a model that modifies the relic abundance of axions by introducing a new light scalar that couples to the Peccei-Quinn field. This new mechanism dynamically alters the effective symmetry-breaking scale and affects the early-time dynamics and late-time abundance of axion dark matter. Our analysis shows that this model can accommodate both lighter and heavier axion dark matter compared to standard treatments.