159 research outputs found
The numerical relativity breakthrough for binary black holes
The evolution of black-hole binaries in vacuum spacetimes constitutes the
two-body problem in general relativity. The solution of this problem in the
framework of the Einstein field equations is a substantially more complex
exercise than that of the dynamics of two point masses in Newtonian gravity,
but it also presents us with a wealth of new exciting physics. Numerical
methods are likely the only method to compute the dynamics of black-hole
systems in the fully non-linear regime and have been pursued since the 1960s,
culminating in dramatic breakthroughs in 2005. Here we review the methodology
and the developments that finally gave us a solution of this fundamental
problem of Einstein's theory and discuss the breakthrough's implication for the
wide range of contemporary black-hole physics.Comment: 34 pages, 5 figures; Invited article for Classical and Quantum
Gravity's "Milestones of General Relativity" series; to match published
versio
NR/HEP: roadmap for the future
Physic in curved spacetime describes a multitude of phenomena, ranging from astrophysics to high-energy physics (HEP). The last few years have witnessed further progress on several fronts, including the accurate numerical evolution of the gravitational field equations, which now allows highly nonlinear phenomena to be tamed. Numerical relativity simulations, originally developed to understand strong-field astrophysical processes, could prove extremely useful to understand HEP processes such as trans-Planckian scattering and gauge–gravity dualities. We present a concise and comprehensive overview of the state-of-the-art and important open problems in the field(s), along with a roadmap for the next years
Resonant-plane locking and spin alignment in stellar-mass black-hole binaries: a diagnostic of compact-binary formation
We study the influence of astrophysical formation scenarios on the
precessional dynamics of spinning black-hole binaries by the time they enter
the observational window of second- and third-generation gravitational-wave
detectors, such as Advanced LIGO/Virgo, LIGO-India, KAGRA and the Einstein
Telescope. Under the plausible assumption that tidal interactions are efficient
at aligning the spins of few-solar mass black-hole progenitors with the orbital
angular momentum, we find that black-hole spins should be expected to
preferentially lie in a plane when they become detectable by gravitational-wave
interferometers. This "resonant plane" is identified by the conditions
\Delta\Phi=0{\deg} or \Delta\Phi=+/-180{\deg}, where \Delta\Phi is the angle
between the components of the black-hole spins in the plane orthogonal to the
orbital angular momentum. If the angles \Delta \Phi can be accurately measured
for a large sample of gravitational-wave detections, their distribution will
constrain models of compact binary formation. In particular, it will tell us
whether tidal interactions are efficient and whether a mechanism such as mass
transfer, stellar winds, or supernovae can induce a mass-ratio reversal (so
that the heavier black hole is produced by the initially lighter stellar
progenitor). Therefore our model offers a concrete observational link between
gravitational-wave measurements and astrophysics. We also hope that it will
stimulate further studies of precessional dynamics, gravitational-wave template
placement and parameter estimation for binaries locked in the resonant plane.Comment: 26 pages, 11 figures, 3 tables, accepted in Physical Review D. 4
movies illustrating resonance locking are available online: for links, see
footnote 8 of the pape
Collisions of charged black holes
We perform fully nonlinear numerical simulations of charged-black-hole collisions, described by the Einstein-Maxwell equations, and contrast the results against analytic expectations. We focus on head-on collisions of nonspinning black holes, starting from rest and with the same charge-to-mass ratio, Q/M. The addition of charge to black holes introduces a new interesting channel of radiation and dynamics, most of which seem to be captured by Newtonian dynamics and flat-space intuition. The waveforms can be qualitatively described in terms of three stages: (i) an infall phase prior to the formation of a common apparent horizon; (ii) a nonlinear merger phase that corresponds to a peak in gravitational and electromagnetic energy; (iii) the ringdown marked by an oscillatory pattern with exponentially decaying amplitude and characteristic frequencies that are in good agreement with perturbative predictions. We observe that the amount of gravitational-wave energy generated throughout the collision decreases by about 3 orders of magnitude as the charge-to-mass ratio Q/M is increased from 0 to 0.98. We interpret this decrease as a consequence of the smaller accelerations present for larger values of the charge. In contrast, the ratio of energy carried by electromagnetic to gravitational radiation increases, reaching about 22% for the maximum Q/M ratio explored, which is in good agreement with analytic predictions
Numerical simulations of single and binary black holes in scalar-tensor theories: circumventing the no-hair theorem
Scalar-tensor theories are a compelling alternative to general relativity and
one of the most accepted extensions of Einstein's theory. Black holes in these
theories have no hair, but could grow "wigs" supported by time-dependent
boundary conditions or spatial gradients. Time-dependent or spatially varying
fields lead in general to nontrivial black hole dynamics, with potentially
interesting experimental consequences. We carry out a numerical investigation
of the dynamics of single and binary black holes in the presence of scalar
fields. In particular we study gravitational and scalar radiation from
black-hole binaries in a constant scalar-field gradient, and we compare our
numerical findings to analytical models. In the single black hole case we find
that, after a short transient, the scalar field relaxes to static
configurations, in agreement with perturbative calculations. Furthermore we
predict analytically (and verify numerically) that accelerated black holes in a
scalar-field gradient emit scalar radiation. For a quasicircular black-hole
binary, our analytical and numerical calculations show that the dominant
component of the scalar radiation is emitted at twice the binary's orbital
frequency.Comment: 21 pages, 6 figures, matches version accepted in Physical Review
Comment on "Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy"
It has been suggested that rotating black holes could serve as particle
colliders with arbitrarily high center-of-mass energy. Astrophysical
limitations on the maximal spin, back-reaction effects and sensitivity to the
initial conditions impose severe limits on the likelihood of such collisions.Comment: Accepted for publication in Physical Review Letters. v2: Published
versio
Head-On collisions of different initial data
We discuss possible origins for discrepancies observed in the radiated
energies in head-on collisions of non-spinning binaries starting from
Brill-Lindquist and superposed Kerr-Schild data. For this purpose, we discuss
the impact of different choices of gauge parameters and a small initial boost
of the black holes.Comment: Proceedings of the Eleventh Marcel Grossmann Meeting; 3 pages (limit
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