(P)reheating and gravitational waves in $\alpha$-attractor models

Abstract

We study post-inflationary evolution in $\alpha$-attractor T-models of inflation. We consider the dynamics of both scalar fields present in these models: the inflaton and the spectator, as a negative field-space curvature may lead to geometrical destabilization of the spectator. We perform state-of-the-art lattice simulations with a dedicated numerical code optimized for those models. We corroborate earlier findings that the perturbations of the spectator field are much more unstable than the perturbations of the inflaton field, so the dynamics of early stages of preheating is dominated by the evolution of spectator perturbations. We also calculate the spectrum of gravitational waves originating from scalar fluctuations in order to determine if the $\alpha$-attractor T-models can be constrained or even ruled out by present cosmological observations, but not by direct searches of gravitational waves.