Axion Inflation Models and Gravitational Waves
Abstract: Axions are important candidates for large field inflation theories since they enjoy the shift symmetry which protects the spoiling of supposed-to-be-flat inflationary potential. Natural Inflation, the first and also the simplest axion inflation model, is one of the most motivated models, but it is not anymore consistent with the current experimental data. One of the most attractive ways to stay in observational bounds and prevent from trans-Planckian excursion in field space is employing multiple axion fields. I will present the results of our analysis related with the one of the most well known models, called aligned natural inflation.
There is a strong effort to detect the primordial gravitational waves (GW) which is motivated by the direct relation between the amplitude of GW signal and the energy scale of inflation, in the standard case of GW production from vacuum. I will discuss the robustness of this relation and present a concrete model employing a coupling between a rolling axion and a gauge field, that can produce a detectable GW signal for a considerably small inflationary energy scales, respecting bounds from back-reaction, perturbativity, and the gaussianity of the measured density perturbations. I will finally discuss the possibility of detecting an inflationary GW signal at terrestrial (AdvLIGO) and space (LISA) interferometers. Such experiments are sensitive to the modes much smaller than the ones corresponding to CMB and Large Scale Structure, presenting a unique observational window on the final stages of inflation.
Reminder: Tea and cookies will be in the seminar room before the seminar.