Constraining the Extra Polarization Modes of Gravitational Waves with Double White Dwarfs

Understand

The detection of gravitational wave (GW) has opened a new window to test the theory of gravity in the strong field regime.

• In general relativity (GR), GW can only possess two tensor polarization modes, which are known as the $+$ and $\times$ modes.
• However, vector and scalar modes can exist in some modified theories of gravity, and we can test the gravitational theories by probing these extra polarization modes.
• As a space-borne GW detector, TianQin will be launched in the 2030s, and it is expected to observe plenty of GW signals, including those from nearly ten-thousands double white dwarfs (DWDs) in our galaxy.