Probing nontensorial gravitational waves with a next-generation ground-based detector network

In general relativity, there are only two polarizations for gravitational waves. However, up to six polarizations are possible in a generic metric theory of gravity. Therefore, measuring the polarization content of gravitational waves provides an efficient way to test theories of gravity. We analyze the sensitivity of a next-generation ground-based detector network to nontensorial polarizations. We present our method to localize gravitational wave signals in the time-frequency domain and construct the model-independent null stream for events with known sky locations. We obtain results based on simulations of binary neutron star mergers in a six-detector network. For a single event at a luminosity distance DL=100 Mpc, at 5σ confidence, the smallest amplitude for detection of scalar and vector modes relative to tensor modes are respectively Aₛ=0.045 and Aᵥ=0.014. For multiple events in an averaged observing run of ten years, the detection limits at 5σ confidence are Aₛ=0.05 and Aᵥ=0.02. If we are fortunate, a few strong events might significantly improve the limits.