Speaker: Edward Broadberry, University of Maryland
Title: Warm Inflation with Pseudo-scalar couplings
Abstract: Inflaton couplings during warm inflation result in the production of a thermal bath. Thermal friction and fluctuations can dominate the standard de Sitter analogues, re- sulting in a modified slow-roll scenario with a new source of density fluctuations. Due to issues with back-reaction, it is advantageous to consider inflaton couplings with the thermal bath that are pseudo-scalar in nature, e.g., derivative interactions or topological F ËœF cou- plings. We demonstrate that every single existing model of warm inflation utilizing pseudo- scalar couplings needs to be corrected to account for the chemical potentials that the thermal bath acquires in response to the inflaton coupling. These chemical potentials are for non- conserved charges, and are non-zero only because of the applied inflaton couplings. The model-dependent chemical potentials modify the fluctuation-dissipation theorem, making the relationship between the thermal friction and thermal fluctuations model-dependent. In ex- treme cases, these chemical potentials can cause the friction term to vanish while thermal fluctuations remain non-zero. In the context of a simple example, we demonstrate how to calculate the chemical potentials, thermal friction, and thermal fluctuations using both the Boltzmann equations and by calculating thermal expectation values, showing explicitly that the two approaches give the same result.