Dilatonic effects on a falling test mass in scalar-tensor theory

TL;DR

This paper investigates how a 4d dilaton field influences the acceleration of a falling test mass within scalar-tensor theories, highlighting significant differences from general relativity in certain parameter regimes.

Contribution

It provides new analytical results for particle accelerations in scalar-tensor theories using exact solutions, comparing them with general relativity.

Findings

Brans-Dicke theory results differ qualitatively from general relativity.

Exact solutions are used to analyze accelerations in weak field approximation.

Differences are significant for certain parameter ranges.

Abstract

Effects of a 4d dilaton field on a falling test mass are examined from the Einstein frame perspective of scalar-tensor theory. Results are obtained for the centripetal acceleration of particles in circular orbits, and the radial acceleration for particles with pure radial motion. These results are applied to the specific case of nonrelativistic motion in the weak field approximation of Brans-Dicke theory, employing the exact Xanthopoulos-Zannias solutions. For a given parameter range, the results obtained from Brans-Dicke theory are qualitatively dramatically different from those of general relativity. Comments are made concerning a comparison with the general relativistic results in the limit of an infinite Brans-Dicke parameter.