A5005948157- Pulsars and Gravitational Waves Research
- Black Holes and Theoretical Physics
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Quantum Electrodynamics and Casimir Effect
- Geophysics and Sensor Technology
- Relativity and Gravitational Theory
- Noncommutative and Quantum Gravity Theories
- Experimental and Theoretical Physics Studies
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Aerodynamics and Acoustics in Jet Flows
- Particle Accelerators and Free-Electron Lasers
- Adaptive optics and wavefront sensing
- Radiative Heat Transfer Studies
- Geomagnetism and Paleomagnetism Studies
- Gamma-ray bursts and supernovae
- Laser-Plasma Interactions and Diagnostics
- High-pressure geophysics and materials
- Superconducting Materials and Applications
- Energy, Environment, Agriculture Analysis
- Advanced Differential Geometry Research
- Acoustic Wave Phenomena Research
- Ocean Waves and Remote Sensing
University of Sheffield
2014-2024
University of Southampton
2010-2013
University of Edinburgh
2012
Universidade Federal do Pará
2010
Universidade de São Paulo
2010
University College Dublin
2007-2009
University of Cambridge
2006
We investigate the instability of massive scalar field in vicinity a rotating black hole. The arises from amplification caused by classical superradiance effect. affects bound states: solutions to Klein-Gordon equation which tend zero at infinity. calculate spectrum state frequencies on Kerr background using continued-fraction method, adapted studies quasinormal modes. demonstrate that is most significant for $l=1$, $m=1$ state, $M\ensuremath{\mu}\ensuremath{\lesssim}0.5$. For fast hole...
Bosonic fields on rotating black hole spacetimes are subject to amplification by superradiance, which induces exponentially-growing instabilities (the `black bomb') in two scenarios: if the is enclosed a mirror, or bosonic field has rest mass. Here we present time-domain study of scalar Kerr spacetime probes ultra-long timescales up $t \lesssim 5 \times 10^6 M$, reveal growth instability. We describe an highly-efficient method for evolving field, based spectral decomposition into coupled set...
We study the propagation of a massive vector or Proca field on Schwarzschild spacetime. The equations are reduced to one-dimensional wave equation for odd-parity part and two coupled even-parity field. use numerical techniques based solving (scalar matrix-valued) three-term recurrence relations compute spectra both quasinormal modes quasibound states, which have no massless analogue, complemented in latter case by forward-integration method. radial analytically near-horizon far-field regions...
Can a black hole that suffers superradiant instability evolve towards ``hairy'' configuration which is stable? We address this question in the context of Einstein-charged scalar field theory. First, we describe family static solutions possess charged scalar-field hair confined within mirror-like boundary. Next, derive set equations govern linear, spherically symmetric perturbations these hairy solutions. present numerical evidence suggests that, unlike vacuum solutions, (single-node) are...
Spinning horizonless compact objects may be unstable against an ``ergoregion instability.'' We investigate this mechanism for electromagnetic perturbations of ultracompact Kerr-like with a reflecting surface, extending previous (numerical and analytical) work limited to the scalar case. derive analytical result frequency instability timescale modes which is valid at small frequencies. argue that our analysis can directly extended gravitational exotic in black-hole limit. The generically...
A massive vector boson field in the vicinity of a rotating black hole is known to suffer an instability, due exponential amplification (co-rotating, low-frequency) bound states by superradiance. Here we calculate state spectrum exploiting separation variables recently achieved Frolov, Krtous, Kubiznak and Santos (FKKS) for Proca on Kerr-(A)dS-NUT spacetimes arbitrary dimension. Restricting 4D Kerr case, first establish relationship between FKKS Teukolsky massless case; obtain exact results...
We present a study of scattering massless planar scalar waves by charged non-rotating black hole. Partial wave methods are applied to compute and absorption cross sections, for range incident wavelengths. compare our numerical results with semi-classical approximations from geodesic analysis, find excellent agreement. The glory in the backward direction is studied, its properties shown be related photon orbit. effects hole charge upon examined detail. As increased, we that section decreases,...
It is well established that the response of a black hole to generic perturbation characterized by spectrum damped resonances, called quasinormal modes; and that, in limit large angular momentum ($l\ensuremath{\gg}1$), mode frequency related properties unstable null orbits. In this paper we develop an expansion method explore link. We obtain new closed-form approximations for lightly part large-$l$ regime. confirm at leading order $l$, resonance linked orbital frequency, damping Lyapunov...
We calculate the effect of self-interaction on ``geodetic'' spin precession a compact body in strong-field orbit around black hole. Specifically, we consider angle $\ensuremath{\psi}$ per radian orbital revolution for particle carrying mass $\ensuremath{\mu}$ and $s\ensuremath{\ll}(G/c){\ensuremath{\mu}}^{2}$ circular Schwarzschild hole $M\ensuremath{\gg}\ensuremath{\mu}$. compute through $\mathcal{O}(\ensuremath{\mu}/M)$ perturbation theory, i.e, including correction...
For a self-gravitating particle of mass $\ensuremath{\mu}$ in orbit around Kerr black hole $M\ensuremath{\gg}\ensuremath{\mu}$, we compute the $\mathcal{O}(\ensuremath{\mu}/M)$ shift frequency innermost stable circular equatorial due to conservative piece gravitational self-force acting on particle. Our treatment is based Hamiltonian formulation dynamics terms geodesic motion certain locally defined effective smooth spacetime. We recover same result using so-called first law binary...
We extend the gravitational self-force approach to encompass `self-interaction' tidal effects for a compact body of mass $\mu$ on quasi-circular orbit around black hole $M \gg \mu$. Specifically, we define and calculate at $O(\mu)$ (conservative) shifts in eigenvalues electric- magnetic-type tensors, (dissipative) shift scalar product between their eigenbases. This yields four gauge-invariant functions, from which one may construct other quantities such as curvature scalars speciality index....
Abstract We construct the metric perturbation in Lorenz gauge for a compact body on circular equatorial orbit of rotating black hole (Kerr) spacetime, using newly-developed method separation variables. The is formed from linear sum differential operators acting Teukolsky mode functions, and certain auxiliary scalars, which are solutions to ordinary equations frequency domain. For radiative modes, solution uniquely determined by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
We study the scattering of massive spin-half waves by a Schwarzschild black hole using analytical and numerical methods. begin extending recent perturbation theory calculation to next order obtain Born series for differential cross section Mott polarization, valid at small couplings. continue deriving an approximation glory spinor particles considering classical timelike geodesics spin precession. Next, we formulate Dirac equation on background, outline simple method finding partial wave...
This is a study of the scattering and absorption planar gravitational waves by Kerr black hole in vacuum. We apply partial wave method to compute cross sections for special case radiation incident along rotation axis. A catalogue numerically-accurate presented, range wavelengths Mω ⩽ 4 rates 0.999M. Three effects are studied detail: polarization, helicity-reversal glory scattering. First, new approximation polarization long-wavelength limit derived. show that distinguishes between...
We calculate the absorption cross section of a massive neutral scalar field impinging upon Reissner-Nordstr\"om black hole. First, we derive key approximations in high- and low-frequency regimes. Next, develop numerical method to compute at intermediate frequencies, present selection results. Finally, draw together our complementary approaches give quantitative full-spectrum description absorption.
This is the third in a series of papers aimed at developing practical time-domain method for self-force calculations Kerr spacetime. The key elements are (i) removal singular part perturbation field with suitable analytic "puncture", (ii) decomposition equations azimuthal ($m$-)modes, taking advantage axial symmetry background, (iii) numerical evolution individual $m$-modes 2+1-dimensions finite difference scheme, and (iv) reconstruction local from mode sum. Here we report first...
We formulate the Dirac equation for a massive neutral spin-half particle on rotating black hole spacetime, and we consider its (quasi)bound states: gravitationally-trapped modes which are regular across future event horizon.These bound states decay with time, due to absence of superradiance in (single-particle) field.We introduce practical method computing spectrum energy levels rates, compare our numerical results known asymptotic small-M µ large-M regimes.By applying perturbation theory...
We investigate the qualitative features of binary black hole shadows using model two extremally charged holes in static equilibrium (a Majumdar--Papapetrou solution). Our perspective is that spacetimes are natural exemplars chaotic scattering, because they admit more than one fundamental null orbit, and thus an uncountably-infinite set perpetual orbits which generate scattering singularities initial data. Inspired by three-disc model, we develop appropriate symbolic dynamics to describe...
We present the gravitational-wave flux balance law in an extreme mass-ratio binary with a spinning secondary. This relates of energy (angular momentum) radiated to null infinity and through event horizon local change secondary's orbital for generic, nonresonant bound orbits Kerr spacetime. As explicit example we compute these quantities spin-aligned body moving on circular orbit around Schwarzschild black hole. perform this calculation both analytically, via high-order post-Newtonian...
Perturbations of Kerr spacetime are typically studied with the Teukolsky formalism, in which a pair gauge invariant components perturbed Weyl tensor expressed terms separable modes that satisfy ordinary differential equations. However, for certain applications it is desirable to construct full metric perturbation Lorenz gauge, linearized Einstein field equations take manifestly hyperbolic form. Here we obtain set Lorenz-gauge solutions vacuum on Kerr-Newman-Unti-Tamburino spacetimes...
We show that a charged, massive scalar field in the vicinity of an electrically-charged Ay\'on-Beato-Garc\'ia (ABG) regular black hole has spectrum quasibound states (in certain parameter regime) grow exponentially with time, due to superradiance. Superradiant are made possible by enhancement electrostatic potential at horizon nonlinear electrodynamics; contrast, Reissner-Nordstr\"om does not possess such superradiant states. Here we compute for range multipoles $\ell$ across space, and find...
We study the absorption of massive spin-half particles by a small Schwarzschild black hole numerically solving single-particle Dirac equation in Painlev\'e-Gullstrand coordinates. calculate cross section $\ensuremath{\sigma}$ over range gravitational couplings $Mm/m_{P}{}^{2}$ and incident particle energies $E$. At high couplings, where radius ${R}_{S}$ is much greater than wavelength $\ensuremath{\lambda}$, we find that $\ensuremath{\sigma}(E)$ approaches classical result for point...
We compute the spectrum of normalizable fermion bound states in a Schwarzschild black hole background. The eigenstates have complex energies. real parts energies, for small couplings, closely follow hydrogenlike spectrum. imaginary give decay times various states, due to absorption properties hole, with closer having shorter half-lives. As coupling increases, departs from that hydrogen atom, as close horizon become unfavorable. Beyond certain $1{S}_{1/2}$ state is no longer ground state,...