Can Decaying Particles Raise the Upperbound on the Peccei-Quinn Scale?
Abstract
We have reexamine the effect of entropy production on the cosmic axion density and find that the Peccei-Quinn scale Fa larger than about 1015~GeV is not allowed even if large entropy is produced by the decays of coherent oscillations or non-relativistic massive particles. We stress that this result is independent of the details of models for the decaying particles.
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