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

Recent work applying the notion of pseudospectrum to gravitational physics showed that quasinormal mode spectrum black holes is unstable, with possible exception longest-lived (fundamental) mode. The fundamental dominates expected signal in wave astronomy, and there no reason why it should have privileged status. We compute two model problems where Schwarzschild potential perturbed by a small "bump" consisting either Pöschl-Teller or Gaussian, we show destabilized under generic...

Black hole spectroscopy is the program to measure complex gravitational wave frequencies of merger remnants, and quantify their agreement with characteristic black holes computed at linear order in perturbation theory. In a ``weaker'' (nonagnostic) version this test, one assumes that depend on mass spin final Kerr as predicted Linear theory expected be good approximation only late times, when remnant close enough stationary hole. However, it has been claimed superposition overtones fixed...

In general relativity, when two black holes merge they produce a rotating (Kerr) hole remnant. According to perturbation theory, the remnant emits ``ringdown'' radiation; superposition of exponentials with characteristic complex frequencies that depend only on remnant's mass and spin. While goal spectroscopy program is measure quasinormal mode frequencies, knowledge their amplitudes phases equally important determine which modes are detectable, possibly perform additional consistency checks....

Black hole spectroscopy with gravitational waves is an important tool to measure the mass and spin of astrophysical black holes test their Kerr nature. Next-generation ground- space-based detectors will observe binary mergers large signal-to-noise ratios perform routinely. It was recently shown that small perturbations due, e.g., environmental effects (the "flea") effective potential governing gravitational-wave generation propagation in exteriors "elephant") can lead arbitrarily changes...

Gravitational-wave (GW) astronomy offers the potential to probe wave-optics regime of gravitational lensing. Wave-optics (WO) effects are relevant at low frequencies, when wavelength is comparable characteristic lensing time delay multiplied by speed light, and thus often negligible for electromagnetic signals. Accurate predictions require computing conditionally convergent diffraction integral, which involves highly oscillatory integrands numerically difficult. We develop implement several...

Just like light, gravitational waves (GWs) are deflected and magnified by fields as they propagate through the Universe. However, their low frequency, phase coherence feeble coupling to matter allow for distinct lensing phenomena, such diffraction central images, that challenging observe electromagnetic sources. Here we explore how these phenomena can be used probe features of lenses. We focus on two variants singular isothermal sphere, with (1) a variable slope density (2) core. describe...

In the aftermath of a binary black hole merger event, gravitational wave signal emitted by remnant is modeled as superposition damped sinusoids known quasinormal modes. While dominant modes originating from linear perturbation theory have been studied extensively in this postmerger ``ringdown'' phase, more accurate models ringdown radiation include nonlinear arising higher-order perturbations spacetime. We explore detectability quadratic with both ground- and space-based next-generation...

In the aftermath of a binary black hole merger event, gravitational wave signal emitted by remnant is modeled as superposition damped sinusoids known quasinormal modes. While dominant modes originating from linear perturbation theory have been studied extensively in this post-merger "ringdown" phase, more accurate models ringdown radiation include nonlinear arising higher-order perturbations spacetime. We explore detectability quadratic with both ground- and space-based next-generation...

ABSTRACT When gravitational waves (GWs) pass through the nuclear star clusters of galactic lenses, they may be microlensed by stars. Such microlensing can cause potentially observable beating patterns on waveform due to superposition and magnify signal. On one hand, magnification could lead first detection a GW. other introduces systematic error in strong lensing use-cases, such as localization cosmography studies. By numerically solving diffraction integral, we show that effects are...

When gravitational waves pass near a gravitating object, they are deflected, or lensed. If the object is massive, such that wavelength of small compared to its size, lensed wave events can be identified when multiple signals detected at different times. However, long, wave-optics diffraction effects will important, and event by looking for frequency-dependent modulations waveform, without having associate signals. For current ground-based detectors observing stellar-mass binary compact...

One class of competitive candidates for dark matter is ultralight bosons. If they exist, these bosons may form long-lived bosonic clouds surrounding rotating black holes via superradiant instabilities, acting as sources gravity and affecting the propagation gravitational waves around host hole. During extreme-mass-ratio inspirals, will survive inspiral phase can affect quasinormal-mode frequencies perturbed black-hole-bosonic-cloud system. In this work, we compute shifts a hole due to...

Black hole spectroscopy is the program to measure complex gravitational-wave frequencies of merger remnants, and quantify their agreement with characteristic black holes computed at linear order in perturbation theory. In a "weaker" (non-agnostic) version this test, one assumes that depend on mass spin final Kerr as predicted Linear theory expected be good approximation only late times, when remnant close enough stationary hole. However, it has been claimed superposition overtones fixed...

ABSTRACT Gravitational lensing describes the bending of trajectories light and gravitational waves due to potential a massive object. Strong by galaxies can create multiple images with different overall amplifications, arrival times, image types. If, furthermore, wave encounters star along its trajectory, microlensing will take place. Previously, it has been shown that effects microlenses on strongly-lensed type-I could be negligible in practice, at least low magnification regime. In this...

Multiple gauge theories predict the presence of cosmic strings with different mass densities Gμ/c2. We derive an equation governing perturbations a rotating black hole pierced by straight, infinitely long string along its axis rotation and calculate quasinormal-mode frequencies such hole. then carry out parameter estimation on first detected gravitational-wave event, GW150914, hypothesizing that there is piercing through remnant, yielding constraint Gμ/c2 <3.8× 10−3 at 90% confidence...

Gravitational lensing describes the bending of trajectories light and gravitational waves due to potential a massive object. Strong by galaxies can create multiple images with different overall amplifications, arrival times, image types. If, furthermore, wave encounters star along its trajectory, microlensing will take place. Previously, it has been shown that effects microlenses on strongly-lensed type-I could be negligible in practice, at least low magnification regime. In this work, we...

Just like light, gravitational waves (GWs) are deflected and magnified by fields as they propagate through the Universe. However, their low frequency, phase coherence feeble coupling to matter allow for distinct lensing phenomena, such diffraction central images, that challenging observe electromagnetic sources. Here we explore how these phenomena can be used probe features of lenses. We focus on two variants singular isothermal sphere, with 1) a variable slope density 2) core. describe...

Gravitational wave (GW) astronomy offers the potential to probe wave-optics regime of gravitational lensing. Wave optics (WO) effects are relevant at low frequencies, when wavelength is comparable characteristic lensing time delay multiplied by speed light, and thus often negligible for electromagnetic signals. Accurate predictions require computing conditionally convergent diffraction integral, which involves highly oscillatory integrands numerically difficult. We develop implement several...

When gravitational waves pass near a gravitating object, they are deflected, or lensed. If the object is massive, such that wavelength of small compared to its size, lensed wave events can be identified when multiple signals detected at different times. However, long, wave-optics diffraction effects will important, and event by looking for frequency-dependent modulations waveform, without having associate signals. For current ground-based detectors observing stellar-mass binary compact...

The wolensing Python package offers a solution for gravitational wave lensing computations within the full wave-optics regime. This tool is primarily designed to calculate amplification factor including diffractive effects, an essential component generating accurate lensed waveforms. These waveforms are integral astrophysical and cosmological studies related gravitational-wave lensing. Integrating with lensingGW (Pagano, Hannuksela, Li 2020), provides solutions image positions in...

In general relativity, when two black holes merge they produce a rotating (Kerr) hole remnant. According to perturbation theory, the remnant emits "ringdown" radiation: superposition of exponentials with characteristic complex frequencies that depend only on remnant's mass and spin. While goal spectroscopy program is measure quasinormal mode frequencies, knowledge their amplitudes phases equally important determine which modes are detectable, possibly perform additional consistency checks....

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