Weak-field regime of the generalized hybrid metric-Palatini gravity

TL;DR

This paper investigates the weak-field behavior of the generalized hybrid metric-Palatini gravity, deriving constraints on its scalar fields by comparing theoretical predictions with observational data.

Contribution

It provides a detailed analysis of the weak-field limit of the theory, including scalar-tensor representation and observational bounds on scalar field parameters.

Findings

Derived effective Newton constant and PPN parameter gamma.

Established bounds on scalar field masses and couplings.

Analyzed specific cases where general methods do not apply.

Abstract

In this work we explore the dynamics of the generalized hybrid metric-Palatini theory of gravity in the weak-field, slow-motion regime. We start by introducing the equivalent scalar-tensor representation of the theory, which contains two scalar degrees of freedom, and perform a conformal transformation to the Einstein frame. Linear perturbations of the metric in a Minkowskian background are then studied for the metric and both scalar fields. The effective Newton constant and the PPN parameter $\gamma$ of the theory are extracted after transforming back to the (original) Jordan frame. Two particular cases where the general method ceases to be applicable are approached separately. A comparison of these results with observational constraints is then used to impose bounds on the masses and coupling constants of the scalar fields.