Gravitational memory effects and the BMS freedoms exhibited at future null infinity have
recently been resolved and utilized in numerical relativity simulations. With this, gravitational …

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 …

We establish a generic, fully relativistic formalism to study gravitational-wave emission by
extreme-mass-ratio systems in spherically symmetric, nonvacuum black hole spacetimes …

Black hole spectroscopy is the program to measure the complex gravitational wave
frequencies of merger remnants, and to quantify their agreement with the characteristic …

We match scattering amplitudes in point particle effective field theory (EFT) and general
relativity to extract low frequency dynamical tidal responses of rotating (Kerr) black holes to …

In general relativity, when two black holes merge they produce a rotating (Kerr) black hole
remnant. According to perturbation theory, the remnant emits “ringdown” radiation; a …

GW190521 is a short-duration, low-frequency gravitational-wave signal in the LIGO-Virgo
catalogue. The signal is consistent with the ringdown and possibly some of the inspiral …

It has been shown, via specific examples and a pseudospectrum analysis, that the black
hole quasinormal spectra are unstable. The implication of such a result for gravitational …

The excitation of quadratic quasinormal modes is an important nonlinear phenomenon for a
Kerr black hole ringing at a specific linear mode. The amplitude of this second-order effect is …

Tidal Love numbers describe the linear response of a compact object under the presence of
external tidal perturbations, and they are found to vanish exactly for black holes within …