Speaker
Description
This talk would be based on the paper by Sebastian Hoof, David J. E. Marsh and myself, that was uploaded on arXiv recently (https://arxiv.org/abs/2108.09563).
We review results from QCD axion string and domain wall simulations and propagate the associ-
ated uncertainties into the calculation of the axion relic density. This allows us to compare different
results in the literature and, using cosmological constraints, to perform statistical inference on the
axion mass window in the post-inflationary Peccei–Quinn symmetry breaking scenario. For dark
matter axions, this leads to a median dark matter axion mass of 0.50 meV, while the 95% cred-
ible interval at highest posterior density is between 0.48 and 0.52 meV. For simulations including
string-domain wall decays, 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 hot dark matter constraints. This demonstrates, at least from
the statistical perspective, that the axion mass can be constrained rather precisely once it is possible
to overcome the much larger systematic uncertainties.
Summary
I present the results from a statistical analysis of the QCD axion mass
for N_DM = 1 including axions from topological defects,
which was done by Sebastian Hoof, David J. E. Marsh and myself. We found
that the axion mass can be constrained rather precisely
once systematic uncertainties are overcome. We further compare two
results of string emission spectrum simulations.
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