Topic: Gravitational waves produced by phase transitions during inflation

Speaker: Assoc. Prof. Haipeng An

Coordinates: PCFT C1124, 16:00, Thursday, Apr. 13

Abstract: During the inflation era, the properties (such as mass and interactions) of the fields coupled to the inflaton field may change substantially. As a result, drastic phenomena, such as phase transitions, may happen. In this talk, I will present simple models that phase transitions can happen and finish during inflation. I will discuss the properties of gravitational wave (GW) signals for first-order phase transitions. I will show a unique oscillatory feature in the GW spectrum. Topological defects, such as domain walls, may be produced for second-order phase transitions. We study the properties of the GWs produced by domain walls during inflation without forming a network. We numerically simulate the domain wall production caused by a second-order phase transition and calculate the GW spectrum using a classical lattice. We show that the GWs produced through first- or second-order phase transitions can be observed directly by future terrestrial and spatial gravitational wave detectors and through the B-mode spectrum in CMB. The signal can also explain the common noise process observed by pulsar timing array experiments. The details of the GW spectrums also contain information about the evolutions of the universe.