Speaker
Wenyuan Ai
Description
First-order phase transitions in the early Universe are a well-motivated source of gravitational
waves (GWs). In this talk, I will discuss a previously overlooked GW production mechanism:
gravitational transition radiation, arising from graviton emission by particles whose mass changes
as they pass through expanding bubble walls. The resulting spectrum features a distinctive shape with a peak frequency redshifting to f_peak ∼ T0 ∼ 10 GHz, where T0 is the current temperature of the Universe. This mechanism is generic and is expected to operate similarly for domain walls and other relativistic interfaces.