Description
The QCD axion is a leading Dark-Matter candidate, typically studied in two cosmological scenarios: a 'post-inflationary' regime, in which axionic cosmic strings form after inflation, and a 'pre-inflationary' regime, in which the axion field is homogenized across the observable Universe and no strings are present. Here I explore a third possibility, in which the axion acquires large fluctuations during the visible part of inflation. This generates a non-standard cosmic-string network, which opens a new window for axion Dark Matter at large axion masses—potentially up to the astrophysical bounds near 0.01 eV, even within the most minimal QCD axion model.
