Reheating the universe after multi-field inflation

Abstract

We study in detail (p)reheating after multi-field inflation models with a particular focus on N-flation. We consider a variety of different couplings between the inflatons and the matter sector, including both quartic and trilinear interactions with a light scalar field. We show that the presence of multiple oscillating inflatons makes parametric resonance inefficient in the case of the quartic interactions. Moreover, perturbative processes do not permit a complete decay of the inflaton for this coupling. In order to recover the hot big bang, we must instead consider trilinear couplings. In this case we show that strong nonperturbative preheating is possible via multi-field tachyonic resonance. In addition, late-time perturbative effects do permit a complete decay of the condensate. We also study the production of gauge fields for several prototype couplings, finding similar results to the trilinear scalar coupling. During the course of our analysis we develop the mathematical theory of the quasi-periodic Mathieu equation, the multi-field generalization of the Floquet theory familiar from preheating after single field inflation. We also elaborate on the theory of perturbative decays of a classical inflaton condensate, which is applicable in single-field models also.

Creation of matter in the universe and groups of type E7

“…It has been recently explained in [5] that in some models of inflation in supergravity which provide an arbitrary inflaton potential [6,7] there is no decay route for the inflaton field, unless one involves the non-minimal vector coupling. An analogous situation with reheating was noticed earlier in the string theory modular inflation models [8][9][10][11] as well as in related supergravity inflation models [12,13]. In [8][9][10][11] it was explained that in string theory standard model particles can live on wrapped D7 branes.…”

“…An analogous situation with reheating was noticed earlier in the string theory modular inflation models [8][9][10][11] as well as in related supergravity inflation models [12,13]. In [8][9][10][11] it was explained that in string theory standard model particles can live on wrapped D7 branes. In such case the inflaton which is the combination of the 4-cycle volume modulus Y and its axionic partner X naturally couple to vectors…”

Inflation and String Theory

“…Investigations in models where the inflaton is a closed string modulus include [562][563][564][565][566].…”

“…Reheating in a string theory model with a shift-symmetric inflaton poses particular difficulties, as explored in [557,560,562,564]. The general issue is that the shift symmetry that protects the inflaton simultaneously limits the couplings of the inflaton to the visible sector.…”

Large Non-Gaussianity in Axion Inflation

“…Sufficient inflation requires Φ > M p which can be achieved for subPlanckian φ i provided √ N is sufficiently large. Typically, the mass basis {φ i } is not aligned with the interaction basis [19,20], so that all φ i couple to a given gauge field as L int = − i α i φ i FF /f i . The coupling of the collective field Φ to FF is highly model-dependent but can be parametrized as L int = −α eff ΦFF /f eff , so that the result of Fig.…”