Poisson-Arago spot for gravitational waves

Understand

For the observer at infinity, a Schwarzschild black hole serves as an attractive opaque disk with a radius of 3$\sqrt{3} M$ that will produce the diffraction pattern of gravitational waves (GWs).

• In this study, we demonstrate that a bright spot, which is a diffraction effect analogous to the Poisson-Arago spot in optics, will appear when an ingoing (quasi-) plane GW is diffracted by a Schwarzschild black hole.
• Here, we propose the diffraction effect of the GWs described by the exact diffraction solution of the GWs using the Heun function.
• For the first time, the Fresnel half-wave zone method is proposed to calculate the angular part of the GW scattering stripes for the observer at infinity.