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 {mathop {{}_sim }limits ^{<}} 10^{-3}. We perform the instability (Floquet) analysis of the linear dynamics and 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.
Highlights
The multiplicity of approaches to reheating and the lack of observables that could at present distinguish between various possibilities have led many authors to consider reheating as an era of the evolution of the Universe that is completely separate from inflation and to include the ignorance about that era into theoretical uncertainties in the predictions of inflationary models. This is because the precise moment at which a given observed CMB mode had left the Hubble radius is related to the subsequent evolution of the Universe, consisting of the (p)reheating period and the part of the RD era until that mode reenters the Hubble radius
The predictions of the inflationary models are often expressed for a range of efolds, typically 50–60, which leads to O(10−2) uncertainty in the determination of ns, comparable with observational uncertainty
We find that the spectator field may have a very strong impact on the post-inflationary dynamics in these models
Summary
The multiplicity of approaches to reheating and the lack of observables that could at present distinguish between various possibilities have led many authors to consider reheating as an era of the evolution of the Universe that is completely separate from inflation and to include the ignorance about that era into theoretical uncertainties in the predictions of inflationary models This is because the precise moment at which a given observed CMB mode had left the Hubble radius (which can be described as the number of e-folds between that instance and the end of inflation) is related to the subsequent evolution of the Universe, consisting of the (p)reheating period and the part of the RD era until that mode reenters the Hubble radius. A more refined way of formulating inflationary predictions consists in considering all reasonable values of
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