Dynamics of test bodies in scalar-tensor theory and equivalence principle

TL;DR

This paper derives the equations of motion for test bodies, including spinning ones, in scalar-tensor gravity theories, confirming the validity of the equivalence principle within this framework.

Contribution

It extends the multipolar equations of motion to scalar-tensor theories, encompassing pointlike and spinning test bodies, and verifies the equivalence principle.

Findings

Equations of motion for pointlike test bodies in scalar-tensor gravity

Equations of motion for spinning test bodies in scalar-tensor gravity

Confirmation of the equivalence principle in scalar-tensor theories

Abstract

How do test bodies move in scalar-tensor theories of gravitation? We provide an answer to this question on the basis of a unified multipolar scheme. In particular, we give the explicit equations of motion for pointlike, as well as spinning test bodies, thus extending the well-known general relativistic results of Mathisson, Papapetrou, and Dixon to scalar-tensor theories of gravity. We demonstrate the validity of the equivalence principle for test bodies.