Inflation and Reheating in Spontaneously Generated Gravity

TL;DR

This paper investigates inflation and reheating within induced gravity models using various potentials, providing analytical solutions and comparing predictions with recent observational data to understand parameter constraints and dynamics.

Contribution

It introduces an analytical approach to reheating dynamics in induced gravity inflation models and compares different potential types against observational constraints.

Findings

Large field inflation allows more parameter flexibility.

Small field inflation imposes stricter constraints, especially on gamma.

Analytical solutions for reheating dynamics were successfully derived.

Abstract

Inflation is studied in the context of induced gravity (IG) $\gamma \sigma^2 R$, where $R$ is the Ricci scalar, $\sigma$ a scalar field and $\gamma$ a dimensionless constant, and diverse symmetry-breaking potentials $V(\sigma)$ are considered. In particular we compared the predictions for Landau-Ginzburg (LG) and Coleman-Weinberg (CW) type potentials and their possible generalizations with the most recent data. We find that large field inflation generally leads to fewer constraints on the parameters and the shape of the potential whereas small field inflation is more problematic and, if viable, implies more constraints, in particular on the parameter $\gamma$. We also examined the reheating phase and obtained an accurate analytical solution for the dynamics of inflaton and the Hubble parameter by using a multiple scale analysis (MSA). The solutions were then used to study the average expansion of the Universe, the average equation of state for the scalar field and both the perturbative and resonant decays of the inflaton field.