Connecting Warm Inflation to Particle Physics: No Sphaleron Heating From a Vanilla Axion

by Sebastian Zell (LMU)

Thursday 17 Oct 2024, 14:00 → 15:00 Europe/Berlin

HS3 (Physikdepartment)

At finite temperature, the coupling of an axion to non-Abelian gauge fields causes dissipation due to sphaleron heating. This mechanism has been considered as ideal for driving inflation in the early Universe since it avoids problematic quantum and thermal corrections. After reviewing these findings, I will show that requiring standard properties of an axion − in particular a discrete shift symmetry and a potential generated non-perturbatively by instanton effects − excludes the strong regime of warm slow-roll inflation, in which thermal friction dominates. While non-minimal (axion-like) models provide a way out, my argument also leaves room for the weak regime of warm axion inflation, but in this case a super-Planckian decay constant represents a well-known issue. As a second aspect, I will point out that a previously discussed suppression of sphaleron heating by light fermions can be easily alleviated in realistic particle physics models.