Polarized Gravitational Waves in Axion Inflation and the Origin of Baryon Asymmetry

In this talk, I will explain the effect of a  non-Abelian gauge field with a small vev in the axion inflation models.  The gauge field

is coupled to the axion with a Chern-Simons interaction and has negligible effect on the background evolution. However, its

quantum fluctuations make significant contribution to the cosmic perturbation.  In particular, the gauge field has a spin-2

fluctuation which explicitly breaks the parity between the left- and right-handed polarization states. That chiral tensor modes are

coupled to the gravitational waves and results in a polarized tensor power spectrum. From the gravitational anomaly in SM, our

setup leads to the gravitational production of lepton number during inflation, sufficient enough to explain the observed matter

asymmetry and the baryon to photon ratio.