Axions, Time Varying CP Violation, and Baryogenesis
  We derive two features of axion cosmology that may have cosmological
implications, whether or not axions are dark matter: For the full range of
allowed axion masses, the evolution of a cosmic axion background allows large
CP violation until temperatures as low as $\sim$ 2 GeV, and once the axion
field begins to oscillate, the cosmological axion field's relaxation to its
ground state can briefly provide a new departure from thermal equilibrium, via
time-varying CP violation. During both of these periods, the Strong CP
violating parameter $\bar\theta$ can be as large as O(1).
