Inflationary axion cosmology

If Peccei-Quinn (PQ) symmetry is broken after inflation, the initial axion angle is a random variable on cosmological scales; based on this fact, estimates of the relic-axion mass density give too large a value if the axion mass is less than about 10^-6 eV. This bound can be evaded if the Universe underwent inflation after PQ symmetry breaking and if the observable Universe happens to be a region where the initial axion angle was atypically small, ₁m₀/ (10^-6 eV^0. 59. ] We show consideration of fluctuations induced during inflation severely constrains the latter alternative.