On preheating in alpha-attractor models of inflation

TL;DR

This paper investigates preheating in alpha-attractor inflation models with two scalar fields, revealing that spectator field perturbations dominate early dynamics, leading to a rapid transition to radiation domination.

Contribution

It provides a detailed Floquet analysis and non-linear lattice simulations of preheating in two-field alpha-attractor models, highlighting the dominant role of spectator perturbations.

Findings

Spectator perturbations are more unstable than inflaton perturbations.

Preheating transition to radiation domination is almost instantaneous.

Spectator field dynamics crucially influence early universe evolution.

Abstract

We study (p)reheating in alpha-attractor T-models of inflation, taking into account both scalar fields present in these models: the inflaton and the spectator. The two-field model has a negative field-space curvature which, at the end of inflation, may lead to geometrical destabilization of the spectator for small values of alpha<~10^(-3). We perform the instability (Floquet) analysis of the linear dynamics and a fully non-linear lattice computations with our numerical code, which we specifically designed for a class of two-field models with non-canonical kinetic terms. We find that the perturbations of the spectator field are much more unstable than the perturbations of the inflaton field, so the dynamics of the early stages of preheating is dominated by the evolution of the spectator perturbations. As a result, the transition from the inflationary era to radiation domination era is practically instantaneous and much faster than previously found in an effective theory including only the inflaton field.