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, 1[ma/(10-6 eV]0.59.] We show consideration of fluctuations induced during inflation severely constrains the latter alternative.
ASJC Scopus subject areas
- Physics and Astronomy(all)