Preheating in Palatini Higgs inflation on the lattice

TL;DR

This paper investigates the preheating process after Higgs inflation in the Palatini gravity framework, demonstrating that tachyonic instability dominates and preheating occurs rapidly within a single oscillation.

Contribution

It provides the first detailed lattice simulation comparison of parametric resonance and tachyonic instability in Palatini Higgs inflation, confirming the dominance of tachyonic preheating.

Findings

Tachyonic instability is the main mechanism for preheating.

Preheating completes within a single Higgs oscillation.

Preheating is consistent with an instantaneous process.

Abstract

We study preheating following Higgs inflation in the Palatini formulation of gravity. We numerically evolve perturbations of the radial mode of the Higgs field and that of three scalars modeling the gauge bosons. We compare the two non-perturbative mechanisms of growth of excitations -- parametric resonance and tachyonic instability -- and confirm that the latter plays the dominant role. Our results provide further evidence that preheating in Palatini Higgs inflation happens within a single oscillation of the Higgs field about the bottom of its potential, consistent with the approximation of an instantaneous preheating.