Warm inflation and Gravitational Waves

Abstract

In this talk we will review the dynamics of warm inflation and the effect of dissipation on the primordial spectrum. When inflation occurs in the so-called strong dissipative regime, this effect will lead to the enhancement of the spectrum over all scales. An in particular to large enough fluctuations over the last 10-20 efolds of inflation which on re-entry may form Primordial Black Holes and act as a source for the tensors at second order. We will discuss different realisations consistent with CMB observations, i.e., different combinations of potentials and dissipative coefficients. Typically the enhancement is maximal near the end of inflation, which result in a spectral density of Gravitational Waves (GW) peaked at large frequencies today, in the range of MHz. Although the frequency range is outside the reach of present and planned GW detectors, it might be reached in future high-frequency gravitational waves detectors, designed to search for cosmological stochastic GW backgrounds above MHz frequencies.