Nonlinear Effects in Black Hole Ringdown

The merger phase of binary black hole coalescences is a transient between an initial oscillating regime (inspiral) and a late exponentially damped phase (ringdown). In spite of the non-linear character of Einstein equations, the merger dynamics presents a surprisingly simple behaviour consistent with effective linearity. On the other hand, energy loss through the event horizon and by scattering to inﬁnity renders the system non-conservative. Hence, the inﬁnitesimal generator of the (effective) linear dynamics is a non-selfadjoint operator. Qualitative features of transients in linear dynamics driven by non-selfadjoint (in general, non-normal) operators are captured by the pseudospectrum of the time generator. We propose the pseudospectrum as a unifying framework to thread together the phases of binary black hole coalescences, from the inspiral-merger transition up to the late quasinormal mode ringdown.

Section: Binary Black Hole Simple Dynamics: Effective Linearitymentioning

confidence: 98%

Section: A Unifying Effective Linear-dynamics Approach To Bbh Dynamic...mentioning

confidence: 99%

Pseudospectrum and binary black hole merger transients

Jaramillo

2022

“…This point of view emphasizes that spacetime from a highly relativistic point of view can be thought of as locally a plane wave, an old idea that should remain useful when taking into account backreaction [17,[99][100][101][102][103]. Given the observational interest to move away from the strict QNM regime toward the merger of black holes [104][105][106][107][108][109], we therefore believe a promising direction of future research is to use the Penrose limit point of view taken here to investigate nonlinear effects. Similarly, it could be of interest in the study of QNM excitation [58,[110][111][112][113][114][115].…”

Section: Discussionmentioning

confidence: 94%

Quasinormal modes from Penrose limits

Fransen

2023

We use Penrose limits to approximate quasinormal modes with large real frequencies. The Penrose limit associates a plane wave to a region of spacetime near a null geodesic. This plane wave can be argued to geometrically realize the geometrical optics approximation. Therefore, when applied to the bound null orbits around black holes, the Penrose limit can be used to study quasinormal modes. For instance, this Penrose limit point of view makes manifest the symmetry that emerges in the geometrical optics approximation of quasinormal modes in terms of isometries of the resulting plane wave spacetime. We apply the procedure to warped AdS3, Schwarzschild black holes and Kerr black holes. In the former we show explicitly how the symmetry algebra contracts to that of the limiting plane wave while in the latter we ﬁnd the expected agreement with numerically computed quasinormal modes for large (real) frequencies.

“…Compare this with the case of gravity. Contrary to Maxwell's equations, Einstein's equations are already nonlinear at the classical level, and nonlinear effects affect phenomena taking place in strong regimes [40,41]. This means that squeezing of macroscopic GWs might well be a natural effect, provided the source is strong enough-which is definitely true in the case of mergers.…”

Section: Are Squeezed Gws Produced In Nature?mentioning

confidence: 99%

The quantum optics of gravitational waves

Abrahão,

Coradeschi,

Micol Frassino

et al. 2023

By utilizing quantum optics techniques, we examine the characteristics of a quantum gravitational wave (GW) signature at interferometers. In particular, we study the problem by analyzing the equations of motion of a GW interacting with an idealized interferometer. Using this method, we reconstruct the classical GW signal from a representation of the quantum version of an almost classical monochromatic wave (a single-mode coherent state), then we discuss the experimental signatures of some specific, more general quantum states. We calculate the observables that could be used at future interferometers to probe possible quantum states carried by the GWs.