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Parametric Decay of the Curvaton

K. Enqvist, S. Nurmi, G. I. Rigopoulos

TL;DR

This paper argues that curvaton decay is most naturally realized through broad parametric resonance, analogous to inflaton preheating but not requiring fine-tuning of couplings. It analyzes a simple two-field–plus–curvaton model where the curvaton excites a bosonic field $\chi$ via a broad resonance, leading to rapid nonperturbative decay and a backreaction-dominated end to resonance. While the linear gravitational-wave background from preheating is typically too small to detect, the nonlinear stages can generate stochastic gravitational waves with potentially observable amplitudes if the inflationary scale is sufficiently low. The work highlights the importance of preheating dynamics for curvaton cosmology and calls for numerical simulations to quantify effects on non-Gaussianities, curvature perturbations, and gravitational-wave signals, with possible connections to supersymmetric models and MSSM flat directions.

Abstract

We argue that the curvaton decay takes place most naturally by way of a broad parametric resonance. The mechanism is analogous to resonant inflaton decay but does not require any tuning of the curvaton coupling strength to other scalar fields. For low scale inflation and a correspondingly low mass scale for the curvaton, we speculate on observable consequences including the possibility of stochastic gravitational waves

Parametric Decay of the Curvaton

TL;DR

This paper argues that curvaton decay is most naturally realized through broad parametric resonance, analogous to inflaton preheating but not requiring fine-tuning of couplings. It analyzes a simple two-field–plus–curvaton model where the curvaton excites a bosonic field via a broad resonance, leading to rapid nonperturbative decay and a backreaction-dominated end to resonance. While the linear gravitational-wave background from preheating is typically too small to detect, the nonlinear stages can generate stochastic gravitational waves with potentially observable amplitudes if the inflationary scale is sufficiently low. The work highlights the importance of preheating dynamics for curvaton cosmology and calls for numerical simulations to quantify effects on non-Gaussianities, curvature perturbations, and gravitational-wave signals, with possible connections to supersymmetric models and MSSM flat directions.

Abstract

We argue that the curvaton decay takes place most naturally by way of a broad parametric resonance. The mechanism is analogous to resonant inflaton decay but does not require any tuning of the curvaton coupling strength to other scalar fields. For low scale inflation and a correspondingly low mass scale for the curvaton, we speculate on observable consequences including the possibility of stochastic gravitational waves

Paper Structure

This paper contains 5 sections, 29 equations, 1 figure.

Table of Contents

  1. Introduction
  2. The inflationary period
  3. The parametric resonance
  4. Gravity waves
  5. Discussion

Figures (1)

  • Figure 1: Comparison of resonant decay of the curvaton in radiation and matter dominated backgrounds. The figure shows $\ln {n}$ for the $\chi$ field in the cases r=1 (dashed lines) as well as $r<1$ (solid lines). It also shows the limits above which backreaction becomes important in both cases. The parameters for these plots are ($M_P=1$), $m=10^{-10}$, $g=10^{-4}$, and $\sigma_*=0.0002$. The onset of backreaction takes place after about 30 - 35 oscillations of the curvaton which corresponds to growth index $\mu \simeq 0.07$.