Constraining the dynamical Chern-Simons gravity with future gravitational wave detectors

TL;DR

The paper tackles testing dynamical Chern-Simons gravity, a parity-violating extension of general relativity, using gravitational-wave inspiral phase measurements. It employs a Fisher-information framework to forecast parameter estimates across a broad detector network (including aLIGO, CE, ET, TianQin, LISA, Taiji, DECIGO, and BBO) and incorporates higher-harmonic modes to model dCS-induced phase shifts. The study finds that space-based detectors alone provide limited constraints, while third-generation ground-based detectors and especially sub-Hertz observatories like DECIGO and BBO could reach kilometer-scale limits on the dCS coupling parameter, particularly when leveraging multi-band observations and realistic BBH populations. Nevertheless, the forecasts are subject to limitations such as inspiral-only modeling, neglect of merger/ringdown, and reliance on Fisher matrix estimates, underscoring the need for more complete waveform modeling and Bayesian analyses in the future.

Abstract

Dynamical Chern-Simons gravity, a parity-violating modification of general relativity, is regarded as a low-energy effective theory arising from string theory. Gravitational waves provide a powerful probe for testing its predictions. However, current gravitational wave observations are unable to place meaningful constraints on this theory through phase measurements, due to limitations from detector noise and the validity requirements of the waveform models. In this paper, we conduct a comprehensive assessment of the prospects for constraining the dynamical Chern-Simons gravity with future gravitational-wave detectors using stellar mass black holes binary. We quantify how the constraining capacities vary across different detectors and source parameters, and identify the regions of parameter space that satisfy the small-coupling condition. Furthermore, by incorporating an astrophysically motivated mass distribution model for stellar mass black hole binaries, we estimate the potential of upcoming observatories.

Figures (3)

• Figure 1: Sensitivities of various detectors.
• Figure 2: Dependence of constraint on $\sqrt{\bar{\alpha}_{\rm dCS}}$ on $M$ for various GW detectors, with stellar mass black holes.
• Figure 3: Dependence of constraint on $\sqrt{\bar{\alpha}_{\rm dCS}}$ on $M$ for multiband observation, with stellar mass black holes.