Exotic axion cosmology in theories with phase transitions below the QCD scale

Phys Rev Lett. 2006 Feb 3;96(4):041301. doi: 10.1103/PhysRevLett.96.041301. Epub 2006 Jan 30.

Abstract

We show that axion phenomenology may be significantly different than conventionally assumed in theories which exhibit late phase transitions (below the QCD scale). In such theories, one can find multiple pseudoscalars with axionlike couplings to matter, including a string scale axion, whose decay constant far exceeds the conventional cosmological bound. Such theories have several dark matter candidates.