Waveform of gravitational waves in the ghost-free parity-violating gravities

TL;DR

This paper investigates how parity-violating extensions of gravity influence gravitational waveforms, revealing amplitude and velocity birefringence effects, and maps these onto the parameterized post-Einsteinian framework.

Contribution

It extends Chern-Simons gravity by including higher derivatives, explicitly calculating GW waveforms with parity violation effects, and mapping these effects onto PPE parameters.

Findings

Velocity birefringence dominates waveform deviations from GR.

Amplitude and phase modifications encode parity violation effects.

Waveform deviations can be characterized within the PPE framework.

Abstract

Gravitational waves (GWs) provide an excellent opportunity to test the gravity in the strong gravitational fields. In this article, we calculate the waveform of GWs, produced by the coalescence of compact binaries, in an extension of the Chern-Simons gravity by including higher derivatives of the coupling scalar field. By comparing the two circular polarization modes, we find the effects of amplitude birefringence and velocity birefringence of GWs in their propagation caused by the parity violation in gravity, which are explicitly presented in the GW waveforms by the amplitude and phase modifications respectively. Combining the two modes, we obtain the GW waveforms in the Fourier domain, and find that the deviations from those in General Relativity are dominated by effects of velocity birefringence of GWs. In addition, we also map the effects of the parity violation on the waveform onto the parameterized post-Einsteinian (PPE) framework and identify explicitly the PPE parameters.