The dark-matter axion mass
  We evaluate the efficiency of axion production from spatially random initial
conditions in the axion field, so a network of axionic strings is present. For
the first time, we perform numerical simulations which fully account for the
large short-distance contributions to the axionic string tension, and the
resulting dense network of high-tension axionic strings. We find nevertheless
that the total axion production is somewhat less efficient than in the
angle-averaged misalignment case. Combining our results with a recent
determination of the hot QCD topological susceptibility (Borsanyi et al 2016),
we find that if the axion makes up all of the dark matter, then the axion mass
is m_a = 26.2 +-3.4 micro-electron volts.
