Gravitational memory effects in Chern-Simons modified gravity

TL;DR

This paper investigates gravitational memory effects within Chern-Simons modified gravity, finding that such effects are similar to general relativity unless the scalar couples directly to matter, and discusses the implications for asymptotic symmetries.

Contribution

It analyzes the nature of gravitational memory effects in Chern-Simons gravity and their relation to asymptotic symmetries, highlighting the absence of new detectable effects from the scalar field.

Findings

Memory effects are similar to GR when the scalar does not couple to matter.

Parity violation appears at higher orders in inverse luminosity radius.

Scalar field does not produce detectable new memory effects.

Abstract

The gravitational memory effects of Chern-Simons modified gravity are considered in the asymptotically flat spacetime. If the Chern-Simons scalar does not directly couple with the ordinary matter fields, there are also displacement, spin and center-of-mass memory effects as in general relativity. This is because the term of the action that violates the parity invariance is linear in the scalar field but quadratic in the curvature tensor. This results in the parity violation occuring at the higher orders in the inverse luminosity radius. The scalar field does not induce any new memory effects that can be detected by interferometers or pulsar timing arrays. The asymptotic symmetry is group is also the extended Bondi-Metzner-Sachs group. The constraints on the memory effects excited by the tensor modes are obtained.