A new PPN parameter to test Chern-Simons gravity

TL;DR

This paper introduces a new PPN parameter in Chern-Simons gravity, which modifies frame dragging and gyroscopic precession, providing a potential experimental test for string theory effects.

Contribution

It identifies a novel PPN parameter specific to Chern-Simons gravity, expanding the framework for testing alternative theories of gravity.

Findings

New PPN term proportional to CS coupling and curl of PPN vector potential

Modification of frame dragging and gyroscopic precession effects

Estimate of the correction size for experimental bounds

Abstract

We study Chern-Simons (CS) gravity in the parameterized post-Newtonian (PPN) framework through a weak-field solution of the modified field equations. We find that CS gravity possesses the same PPN parameters as general relativity, except for the inclusion of a new term, proportional to the CS coupling and the curl of the PPN vector potential. This new term leads to a modification of frame dragging and gyroscopic precession and we provide an estimate of its size. This correction might be used in experiments, such as Gravity Probe B, to bound CS gravity and test string theory.