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 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, ≲[/( eV.] We show consideration of fluctuations induced during inflation severely constrains the latter alternative.
- Received 26 September 1990
- Published in the issue dated 7 January 1991
© 1991 The American Physical Society