Inflation and reheating in scale-invariant scalar-tensor gravity

TL;DR

This paper investigates a scale-invariant scalar-tensor gravity model, analyzing inflation and reheating processes, and compares theoretical predictions with recent observational data to understand early universe dynamics.

Contribution

It provides a detailed analysis of inflation and reheating in a scale-invariant model, including Einstein frame calculations and observational comparisons.

Findings

Symmetry breaking generates a fundamental mass scale.

Reheating occurs via oscillations amplifying Standard Model fields.

Model predictions align with recent cosmological observations.

Abstract

We consider the scale-invariant inflationary model studied in [1]. The Lagrangian includes all the scale-invariant operators that can be built with combinations of $R$, $R^2$ and one scalar field. The equations of motion show that the symmetry is spontaneously broken after an arbitrarily long inflationary period and a fundamental mass scale is generated. Upon symmetry breaking, and in the Jordan frame, both Hubble function and the scalar field undergo damped oscillations that can eventually amplify Standard Model fields and reheat the Universe. In the present work, we study in detail inflation and the reheating mechanism of this model in the Einstein frame and we compare some of the results with the latest observational data.