Thermal axion production
  We reconsider thermal production of axions in the early universe, including
axion couplings to all Standard Model (SM) particles. Concerning the axion
coupling to gluons, we find that thermal effects enhance the axion production
rate by a factor of few with respect to previous computations performed in the
limit of small strong gauge coupling. Furthermore, we find that the top Yukawa
coupling induces a much larger axion production rate, unless the axion couples
to SM particles only via anomalies.
