Inflationary dynamics and preheating of the non-minimally coupled inflaton field in the metric and Palatini formalisms

TL;DR

This paper compares inflationary dynamics and preheating processes of a non-minimally coupled inflaton in metric and Palatini formalisms, revealing differences in scalar field evolution, resonance behavior, and energy transfer efficiency.

Contribution

It provides a detailed comparison of inflation and preheating in metric and Palatini formalisms, highlighting how the formalism affects resonance structures and energy transfer.

Findings

End-of-inflation scalar field value differs between formalisms.

Resonance bands become broader in the metric formalism with increasing ||.

Energy transfer efficiency increases with ||, faster in the metric formalism.

Abstract

The inflationary dynamics and preheating in a model with a non-minimally coupled inflaton field in the metric and Palatini formalisms are studied in this paper. We find that in both formalisms, irrespective of the initial conditions, our Universe will evolve into a slow-roll inflationary era and then the scalar field rolls into an oscillating phase. The value of the scalar field at the end of the inflation in the Palatini formalism is always larger than that in the metric one, which becomes more and more obvious with the increase of the absolute value of the coupling parameter $|\xi|$. During the preheating, we find that the inflaton quanta are produced explosively due to the parameter resonance and the growth of inflaton quanta will be terminated by the backreaction. With the increase of $|\xi|$, the resonance bands gradually close to the zero momentum ($k=0$), and the structure of resonance changes and becomes broader and broader in the metric formalism, while, it remains to be narrow in the Palatini formalism. The energy transfer from the inflaton field to the fluctuation becomes more and more efficient with the increase of $|\xi|$, and in the metric formalism the growth of the efficiency of energy transfer is much faster than that in the Palatini formalism. Therefore, the inflation and preheating show different characteristics in different formalisms.