Preheating with non-minimally coupled scalar fields in higher-curvature inflation models

TL;DR

This paper investigates how non-minimally coupled scalar fields can efficiently preheat in higher-curvature inflation models, especially in $R^2$ and $R^4$ models, revealing conditions for maximal fluctuations and growth rates.

Contribution

It introduces a detailed analysis of parametric preheating with non-minimal coupling in higher-curvature inflation models, highlighting the effects of coupling strength on fluctuation growth.

Findings

Efficient preheating occurs for small coupling values in $R^2$-inflation.

Maximal fluctuation for $R^2$ model is approximately 2×10^{17} GeV.

Preheating in $R^4$ model yields maximal fluctuation around 8×10^{16} GeV.

Abstract

In higher-curvature inflation models ($R+\alpha_n R^n$), we study a parametric preheating of a scalar field $\chi$ coupled non-minimally to a spacetime curvature $R$ ($\xi R \chi^2$). In the case of $R^2$-inflation model, efficient preheating becomes possible for rather small values of $\xi$, i.e. $|\xi|< several. Although the maximal fluctuation $\sqrt{< \chi^2 >}_{max} \approx 2 \times10^{17}$ GeV for $\xi \approx -4$ is almost the same as the chaotic inflation model with a non-minimally coupled $\chi$ field, the growth rate of the fluctuation becomes much larger and efficient preheating is realized. We also investigate preheating for $R^4$ model and find that the maximal fluctuation is $\sqrt{< \chi^2 >}_{max} \approx 8 \times 10^{16}$ GeV for $\xi \approx -35$.