We reanalyze the conditions under which we have a primordial thermal population of axions. We extend a previous study and take into account processes involving gluons and quarks. We conclude that if the Peccei-Quinn scale satisfies Fa<1.2×1012 GeV there is thermal axion production. In this case, a period in the early universe exists where axions would interact with the QCD plasma and we point out that nonthermal axions produced before the end of this period would thermalize.
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|Publication status||Published - 15 Jul 2002|