Nonlinear Effects in Black Hole Ringdown

Phys Rev Lett. 2023 Feb 24;130(8):081401. doi: 10.1103/PhysRevLett.130.081401.


We report evidence for nonlinear modes in the ringdown stage of the gravitational waveform produced by the merger of two comparable-mass black holes. We consider both the coalescence of black hole binaries in quasicircular orbits and high-energy, head-on black hole collisions. The presence of nonlinear modes in the numerical simulations confirms that general-relativistic nonlinearities are important and must be considered in gravitational-wave data analysis.