Cosmic implications of a low-scale solution to the axion domain wall problem

Understand

The post-inflationary breaking of Peccei-Quinn (PQ) symmetry can lead to the cosmic domain wall catastrophe.

• In this Letter we show how to avoid domain walls implementing the Instanton Interference Effect (IIE) with a new interaction which itself breaks PQ symmetry and confines at an energy scale smaller than $\Lambda_{QCD}$.
• We give a general description of the mechanism and consider its cosmological implications and constraints within a minimal model.
• Contrary to other mechanisms we do not require an inverse phase transition neither fine-tuned bias terms.