Oscillating chiral tensor spectrum from axionic inflation

by Ippei Obata (Kyoto University)

Monday 5 Sept 2016, 16:30 → 17:30 Europe/Berlin

seminar room 2, building 2A (DESY Hamburg)

A string axion is one of the best-motivated candidates of inflation due to its shift symmetry, which is nearly broken by quantum non-perturbative effects such as instantons, generating periodic potentials. Remarkably, this kind of potential gives the small oscillatory modulation to the scalar power spectrum, while that of tensor spectrum has been overlooked. In this talk, we discuss the axionic inflation with a modulated potential and examine if the primordial tensor spectrum exhibits oscillatory feature, which is testable with future space-based gravitational wave experiments such as DECIGO and BBO. We found that, in the case of axionic inflation where axion is coupled to the gauge field, it turns out that the sizable oscillation in the tensor spectrum can occur due to the enhancement of chiral gravitational waves sourced by the gauge field. We expect that this feature will be a new probe to axion phenomenologies in early universe through the chiral gravitational waves.