On Inflation and Reheating Features in the Higgs-$R^2$ Model

TL;DR

This paper explores inflation and reheating in the Higgs-$R^2$ model, analyzing the effects of the non-minimal coupling $\xi$ on non-gaussianity, preheating dynamics, and reheating temperature, with implications for dark matter and early universe conditions.

Contribution

It introduces a detailed analysis of inflation and reheating in the Higgs-$R^2$ model, including the impact of $\xi$ on non-gaussianity and the division of preheating into quadratic and quartic regimes.

Findings

$\xi$ cannot produce large non-gaussianity.

Reheating temperature can reach $ imes 10^{10}$ GeV for $\xi<4.2$.

Reheating temperature is about $ imes 10^{9}$ GeV for $\xi>4.2$.

Abstract

We investigated inflation in the Higgs-$R^2$ model and assumed the trajectory to follow a single-field approximation called minimal two-field mode. Using this approximation, we tried to constrain the Higgs' non-minimal coupling $\xi$. During inflation, we investigated the effect of $\xi$ on the non-gaussianity. We found that $\xi$ could not provide the large non-gaussianity. In this paper, we divided the preheating stage to be quadratic regime and quartic regime. During the quadratic regime, the gauge bosons' production is the most dominant. However, it could not drain the whole inflaton's energy. Thus, we introduced a dark matter candidate with a large coupling that could drain the whole inflaton's energy. We also found that if $\xi<4.2$, the oscillation on the quadratic regime continued to the quartic regime. The reheating temperature obtained by this mode can be reached to be $\sim 10^{10}$ GeV and strongly depends on the remaining inflaton's energy density. On contrary, if $\xi>4.2$, the oscillation only happens at the quadratic regime. As we assumed the Pauli exclusion principle does exist during the quadratic regime, the instant decay of gauge bosons to fermions is restricted. Hence we expected, the reheating temperature to be low for about $\sim 10^9$ GeV.