Axions in Japan

Session

Parallel session - Theory I

10 Nov 2025, 15:30

Lecture Hall (Kavli IPMU)

Conveners

Parallel session - Theory I

• Chair: Qiuyue Liang

13. Resolving the QCD Axion Domain Wall Problem with a Light Axion

Kai Murai

10/11/2025, 15:30

We propose two novel solutions to the domain wall problem of the QCD axion by introducing a massless or light axion that also couples to gluons. The first solution applies when the new axion forms strings after inflation. Due to its mixing with the QCD axion, domain walls of the QCD axion are bounded by these strings and confined into cosmologically safe string bundles. This scenario predicts...

14. A Step in Flux to Suppress Axion Isocurvature

Priyesh Chakraborty

10/11/2025, 15:50

The QCD axion is one of the most compelling dark matter candidates, but faces a stringent isocurvature constraint, which requires a relatively low Hubble scale during inflation. If the axion was heavier than the Hubble scale during inflation, its isocurvature is suppressed and the constraint significantly relaxes. We point out a novel mechanism for achieving this, relying on the topological...