# Gravitational Plane Waves in a Non-Riemannian Description of Brans-Dicke Gravity

## TL;DR

This paper explores gravitational plane waves within a non-Riemannian framework of Brans-Dicke gravity, deriving equations of motion and analyzing scalar field effects on test particles.

## Contribution

It introduces a non-Riemannian variational formulation of Brans-Dicke theory and examines gravitational waves using pp-wave metrics in this setting.

## Key findings

- Derived geodesic and autoparallel equations in non-Riemannian Brans-Dicke gravity.
- Analyzed the influence of scalar field gradients on particle motion and deviations.
- Discussed the implications of non-Riemannian geometry on gravitational wave propagation.

## Abstract

The variational field equations of Brans-Dicke scalar-tensor theory of gravitation are given in a non-Riemannian setting in the language of exterior differential forms over 4-dimensional spacetime. The class of pp-wave metrics together with the Brans-Dicke scalar field are used to derive the geodesic and autoparallel equations of motion for non-spinning test masses in Brinkmann and Rosen coordinates. The effects of the gradient of the scalar field on the auto-parallel equations of motion and Jacobi deviation equation are discussed.