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

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 parametrized post-Einsteinian (PPE) framework and identify explicitly the PPE parameters.