Strong-coupling scale and frame-dependence of the initial conditions for chaotic inflation in models with modified (coupling to) gravity

TL;DR

This paper examines how initial conditions for chaotic inflation are constrained by quantum and gravitational considerations, focusing on frame-dependence in models with modified gravity such as $R^2$- and Higgs-inflation.

Contribution

It highlights the upper limit on quantum contributions to energy density and analyzes how initial conditions vary with metric frame in modified gravity inflation models.

Findings

Quantum contributions are bounded by weak-coupling limits.

Initial conditions depend on the choice of metric frame.

The analysis applies broadly to $F(R)$-gravity and non-minimal scalar couplings.

Abstract

A classical evolution in chaotic inflationary models starts at high energy densities with semi-classical initial conditions presumably consistent with universal quantum nature of all the fundamental forces. That is each quantum contributes the same amount to the energy density. We point out the upper limit on this amount inherent in this approach, so that all the quanta are inside the weak-coupling domain. We discuss this issue in realistic models with modified gravity, $R^2$- and Higgs-inflations, emphasizing the specific change of the initial conditions with metric frame, while all the quanta still contribute equal parts. The analysis can be performed straightforwardly in any model with modified gravity ($F(R)$-gravity, scalars with non-minimal couplings to gravity, etc).