Cosmic implications of a low-scale solution to the axion domain wall
  problem
  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. Incidentally, the mechanism leads to
the introduction of new self-interacting dark matter candidates and the
possibility of producing gravitational waves in the frequency range of SKA.
Unless a fine-tuned hidden sector is introduced, the mechanism predicts a QCD
axion in the mass range $1\text{ meV}-15\text{ meV}$.
