Analytical study of mode coupling in hybrid inflation

Abstract

We provide an analytical study of the coupling of short and long wavelength fluctuation modes during the initial phase of reheating in two field models like hybrid inflation. In these models, there is -at linear order in perturbation theory -an instability in the entropy modes of cosmological perturbations which, if not cut off, could lead to curvature fluctuations which exceed the current observational values. Here, we demonstrate that the back-reaction of short wavelength fluctuations is too weak to lead to a truncation of the instability for the long wavelength modes on time scales comparable to the typical instability time scale of the long wavelength entropy modes. Hence, unless there are other mechanisms which truncate the instability, then in models such as hybrid inflation the curvature perturbations produced during reheating on scales of current observational interest may be very important.PACS numbers: 98.80.Cq

Nonperturbative dynamics of reheating after inflation: A review

“…Mode-mode coupling and other forms of nonlinear interactions begin to dominate, which can transfer power between modes of different wavenumbers. 33,36,51,[60][61][62][63]105 To address the behavior of fields after such mode coupling begins, we need to turn to a nonlinear analysis and numerical simulations, and will be discussed in Section 4.…”

Curvature perturbation and waterfall dynamics in hybrid inflation

“…To address this let us first estimate the minimum e-foldings required between the transition time and the time of horizon crossing of the large scale (CMB) modes. We would like to impose the following constraint on the amplitude of these modes 12) in which k CMB is the momentum of cosmological sizes observed on CMB. By using Eq.…”

“…Recently there has been a revival of interest in hybrid inflation [5,6], specifically the dynamics of waterfall field and whether or not significant large scale curvature perturbations can be produced during the waterfall phase transition [7][8][9][10][11][12], for earlier works see also [13][14][15][16]. In this work we search the parameter space of hybrid inflation in details and study the effects of the waterfall field dynamics carefully.…”

Large-scale perturbations from the waterfall field in hybrid inflation

“…However it was recently suggested [8,9] that non-adiabatic large-scale perturbations in the waterfall field could play an important role, in particular leading to non-Gaussian curvature perturbations [8], since these long wavelength modes experience the most rapid growth due to the tachyonic instability in the waterfall field at the end of inflation. It is known that a slow transition during hybrid inflation, allowing inflation to continue for some period after the tachyonic instability, could lead to large curvature perturbations on scales which leave the horizon around the time of the instability [10,11].…”