Hyperextended Scalar-Tensor Gravity

TL;DR

This paper investigates a broad class of Scalar-Tensor theories with arbitrary coupling functions and gravitational constants, analyzing their field equations and cosmological solutions, including cases without analytical inverses.

Contribution

It provides a comprehensive analysis of scalar-tensor theories with arbitrary functions, including their field equations and classification of solutions based on scalar field behavior.

Findings

Different theories can be grouped into classes with identical scalar field solutions.

The paper derives the full set of field equations for these generalized theories.

It explores the cosmological implications of hyperextended scalar-tensor models.

Abstract

We study a general Scalar-Tensor Theory with an arbitrary coupling funtion $\omega (\phi )$ but also an arbitrary dependence of the ``gravitational constant'' $G(\phi )$ in the cases in which either one of them, or both, do not admit an analytical inverse, as in the hyperextended inflationary scenario. We present the full set of field equations and study their cosmological behavior. We show that different scalar-tensor theories can be grouped in classes with the same solution for the scalar field.