Curvature Perturbations from Higgs Modulated Reheating

TL;DR

This paper analyzes how Higgs field fluctuations during reheating can generate curvature perturbations and non-Gaussianity, emphasizing the importance of non-perturbative methods for accurate predictions.

Contribution

It introduces and compares three methods for calculating curvature perturbations, highlighting the effectiveness of the non-perturbative δN formalism in Higgs modulated reheating.

Findings

Non-perturbative δN method provides reliable estimates across various regimes.

Smaller Higgs self-coupling increases curvature perturbations.

Non-Gaussianity is mainly of local shape.

Abstract

In this work we investigate curvature perturbations and non-Gaussianity arising from Higgs modulated reheating in the early Universe. We employ three different methods -- the period-averaging (PA) method, the exact method, and the non-perturbative $\delta N$ formalism -- to compute the power spectrum and bispectrum of curvature perturbations. Our results show that the non-perturbative $\delta N$ method provides a reliable estimate across a wide range of reheating time and Higgs field values, including regimes where the Higgs field oscillates significantly after inflation. We find that a smaller Higgs self-coupling ($\lambda$) leads to a larger curvature perturbation, with the non-Gaussianity predominantly taking a local shape. This highlights the importance of considering non-perturbative effects in calculating the curvature perturbation during Higgs modulated reheating, especially for smaller values of $\lambda$. Our findings offer valuable insights into the dynamics of reheating and the generation of primordial perturbations in the early Universe.