Generalized Slow Roll Conditions and the Possibility of Intermediate Scale Inflation in Scalar-Tensor Theory

TL;DR

This paper derives generalized slow roll conditions for scalar-tensor theories and explores the possibility of intermediate scale inflation, showing it depends on the frame of realization (Jordan vs Einstein).

Contribution

It provides a unified framework for slow roll conditions in scalar-tensor theories and analyzes conditions for intermediate scale inflation in a specific toy model.

Findings

Intermediate scale inflation possible in Jordan frame with Higgs potential

Inflation does not occur at intermediate scales in Einstein frame

Results depend on the choice of gravitational frame

Abstract

Generalized slow roll conditions and parameters are obtained for a general form of scalar-tensor theory (with no external sources), having arbitrary functions describing a nonminimal gravitational coupling F(\phi), a Kahler-like kinetic function k(\phi), and a scalar potential V(\phi). These results are then used to analyze a simple toy model example of chaotic inflation with a single scalar field \phi and a standard Higgs potential and a simple gravitational coupling function. In this type of model inflation can occur with inflaton field values at an intermediate scale of roughly 10^{11} GeV when the particle physics symmetry breaking scale is approximately 1 TeV, provided that the theory is realized within the Jordan frame. If the theory is realized in the Einstein frame, however, the intermediate scale inflation does not occur.