Testing Chern-Simons modified gravity with observations of extreme-mass-ratio binaries

TL;DR

This paper investigates how space-based gravitational wave detectors like LISA can test Chern-Simons modified gravity by analyzing signals from extreme-mass-ratio inspirals, which encode black hole spacetime features.

Contribution

It provides a parameter estimation study demonstrating the potential of EMRI observations to distinguish between General Relativity and Chern-Simons gravity.

Findings

LISA could differentiate GR from CS gravity using EMRI signals.

EMRI waveforms contain signatures sensitive to modifications in gravity theories.

The study advances methods for testing alternative gravity theories with gravitational wave data.

Abstract

Extreme-Mass-Ratio Inspirals (EMRIs) are one of the most promising sources of gravitational waves (GWs) for space-based detectors like the Laser Interferometer Space Antenna (LISA). EMRIs consist of a compact stellar object orbiting around a massive black hole (MBH). Since EMRI signals are expected to be long lasting (containing of the order of hundred thousand cycles), they will encode the structure of the MBH gravitational potential in a precise way such that features depending on the theory of gravity governing the system may be distinguished. That is, EMRI signals may be used to test gravity and the geometry of black holes. However, the development of a practical methodology for computing the generation and propagation of GWs from EMRIs in theories of gravity different than General Relativity (GR) has only recently begun. In this paper, we present a parameter estimation study of EMRIs in a particular modification of GR, which is described by a four-dimensional Chern-Simons (CS) gravitational term. We focus on determining to what extent a space-based GW observatory like LISA could distinguish between GR and CS gravity through the detection of GWs from EMRIs.