Speaker
Description
The QCD axion arises as the pseudo-Goldstone mode of a spontaneously broken abelian Peccei-Quinn (PQ) symmetry. If the scale of PQ symmetry breaking occurs below the inflationary reheat temperature and the domain wall number is unity, then there is a unique axion mass that gives the observed dark matter (DM) abundance. Computing this mass has been the subject of intensive numerical simulations for decades since the mass prediction informs laboratory experiments. In this talk, I will present the most precise and accurate large-scale simulations to date of the axion-string network leveraging adaptive mesh refinement. Accounting for axion production from strings prior to the QCD phase transition leads us to predict that the axion mass should be approximately ma ∈ (45, 65) µeV. However, we provide preliminary evidence that axions are produced in greater quantities from the string-domain-wall network collapse during the QCD phase transition, potentially increasing the mass prediction to as much as 300 µeV.
