Speaker: Ippei Obata (Kyoto Univ)
String axion is one of the best-motivated candidates of inflaton due to its shift symmetry, which is nearly broken by quantum non-perturbative effects such as instantons, generating inflationary potentials. In addition to that, axion generally couples to gauge fields due to the anomaly cancellation mechanism in higher dimensional space-time. Intriguingly, such axion-gauge interactions enhance one helicity mode of gauge fields due to a tachyonic instability and provide chiral gravitational waves during inflation. This novel feature could be a new window to probe high energy physics in early Universe. In this talk, we try to explain its mechanism in the case of both Abelian and non-Abelian gauge fields and explore the testability of chiral primordial gravitational waves with future gravitational wave interferometers.
Place: Room P8, Mathematical Building