The Quality/Cosmology Tension for a Post-Inflation QCD Axion

Post-inflationary QCD axions offer potentially predictive dark-matter models, but protecting the relevant symmetry against quantum-gravity effects can create cosmological problems. This seminar starts with a discrete-symmetry example linking axion quality to domain walls, then examines more elaborate proposals. It explores why nonstandard cosmic histories could change the predicted dark-matter axion mass.