Statistical Uncertainties of the $N_\text{DW} = 1$ QCD Axion Mass Window
  from Topological Defects
  We review results from QCD axion string and domain wall simulations and
propagate the associated uncertainties, including QCD uncertainties, into the
calculation of the axion relic density. We compare two different sets of
studies and, using cosmological constraints, perform statistical inference on
the axion mass window in the post-inflationary Peccei-Quinn symmetry breaking
scenario. For dark matter axions in recent simulations inferring a moderately
infrared-dominated spectrum, this leads to a median dark matter axion mass of
0.50 meV, while the 95% credible interval at highest posterior density is
between 0.48 and 0.52 meV. For alternative simulations including in addition
string-domain wall decays (but with different overall inference on the
spectrum), these numbers are 0.22 meV and [0.16, 0.27] meV. Relaxing the
condition that axions are all of the dark matter, the axion mass window is
completed by an upper bound of around 80 meV, which comes from dark radiation
constraints. This confirms that the axion mass can be constrained rather
precisely regarding statistical uncertainties and further calls for a more
detailed analysis of the various sources of systematic uncertainties plaguing
the simulations.
