The role of chiral gravitational anomaly in cosmology
|講演者||粂 潤哉 氏 （東京大学大学院理学系研究科附属ビッグバン宇宙国際研究センター）|
Quantum anomaly is ubiquitous and investigated in various fields of physics, including cosmology. In this talk, I introduce two interesting phenomena in the early universe caused by the chiral gravitational anomaly, which relates the left-right asymmetry of the fermions and the helicity of the gravitational waves. The first one is so-called "gravitational leptogenesis" where the primordial lepton asymmetry is produced as a consequence of this anomaly in models of inflation generating helical primordial gravitational waves. I show the difficulties in the minimal model of gravitational leptogenesis and briefly discuss the extended models where the gauge fields are involved. The other one is what we call "chiral gravitational effect"(CGE), which can be understood as the gravitational counterpart of the chiral magnetic effect (CME). In these effects, the primordial chiral asymmetry, which can be generated in well-motivated scenarios like GUT baryogenesis, is a key ingredient. I present how CGE affects the primordial gravitational waves propagating in the chiral primordial plasma, while comparing with the CME.