Testing the nature of gravitational-wave polarizations using strongly lensed signals

Understand

Gravitational-wave (GW) observations by a network of ground-based laser interferometric detectors allow us to probe the nature of GW polarizations.

• This would be an interesting test of general relativity (GR), since GR predicts only two polarization modes while there are theories of gravity that predict up to six polarization modes.
• The ability of GW observations to probe the nature of polarizations is limited by the available number of linearly independent detectors in the network.
• (To extract all polarization modes, there should be at least as many detectors as the polarization modes.) Strong gravitational lensing of GWs offers a possibility to significantly increase the effective number of detectors in the network.