58 research outputs found
Nut-charged black holes in matter-coupled N=2, D=4 gauged supergravity
Using the results of arXiv:0804.0009, where all timelike supersymmetric
backgrounds of N=2, D=4 matter-coupled supergravity with Fayet-Iliopoulos
gauging were classified, we construct genuine nut-charged BPS black holes in
AdS_4 with nonconstant moduli. The calculations are exemplified for the
SU(1,1)/U(1) model with prepotential F=-iX^0X^1. The resulting supersymmetric
black holes have a hyperbolic horizon and carry two electric, two magnetic and
one nut charge, which are however not all independent, but are given in terms
of three free parameters. We find that turning on a nut charge lifts the flat
directions in the effective black hole potential, such that the horizon values
of the scalars are completely fixed by the charges. We also oxidize the
solutions to eleven dimensions, and find that they generalize the geometry
found in hep-th/0105250 corresponding to membranes wrapping holomorphic curves
in a Calabi-Yau five-fold. Finally, a class of nut-charged Nernst branes is
constructed as well, but these have curvature singularities at the horizon.Comment: 21 pages, no figures, uses JHEP3.cl
Overspinning a Kerr black hole: the effect of self-force
We study the scenario in which a massive particle is thrown into a rapidly
rotating Kerr black hole in an attempt to spin it up beyond its extremal limit,
challenging weak cosmic censorship. We work in black-hole perturbation theory,
and focus on non-spinning, uncharged particles sent in on equatorial orbits. We
first identify the complete parameter-space region in which overspinning occurs
when back-reaction effects from the particle's self-gravity are ignored. We
find, in particular, that overspinning can be achieved only with particles sent
in from infinity. Gravitational self-force effects may prevent overspinning by
radiating away a sufficient amount of the particle's angular momentum
("dissipative effect"), and/or by increasing the effective centrifugal
repulsion, so that particles with suitable parameters never get captured
("conservative effect"). We analyze the full effect of the self-force, thereby
completing previous studies by Jacobson and Sotiriou (who neglected the
self-force) and by Barausse, Cardoso and Khanna (who considered the dissipative
effect on a subset of orbits). Our main result is an inequality, involving
certain self-force quantities, which describes a necessary and sufficient
condition for the overspinning scenario to be overruled. This "censorship"
condition is formulated on a certain one-parameter family of geodesics in an
extremal Kerr geometry. We find that the censorship condition is insensitive to
the dissipative effect (within the first-order self-force approximation used
here), except for a subset of perfectly fine-tuned orbits, for which a separate
censorship condition is derived. We do not obtain here the self-force input
needed to evaluate either of our two conditions, but discuss the prospects for
producing the necessary data using state-of-the-art numerical codes.Comment: 25 pages, 4 figure
Self-force as a cosmic censor in the Kerr overspinning problem
It is known that a near-extremal Kerr black hole can be spun up beyond its
extremal limit by capturing a test particle. Here we show that overspinning is
always averted once back-reaction from the particle's own gravity is properly
taken into account. We focus on nonspinning, uncharged, massive particles
thrown in along the equatorial plane, and work in the first-order self-force
approximation (i.e., we include all relevant corrections to the particle's
acceleration through linear order in the ratio, assumed small, between the
particle's energy and the black hole's mass). Our calculation is a numerical
implementation of a recent analysis by two of us [Phys.\ Rev.\ D {\bf 91},
104024 (2015)], in which a necessary and sufficient "censorship" condition was
formulated for the capture scenario, involving certain self-force quantities
calculated on the one-parameter family of unstable circular geodesics in the
extremal limit. The self-force information accounts both for radiative losses
and for the finite-mass correction to the critical value of the impact
parameter. Here we obtain the required self-force data, and present strong
evidence to suggest that captured particles never drive the black hole beyond
its extremal limit. We show, however, that, within our first-order self-force
approximation, it is possible to reach the extremal limit with a suitable
choice of initial orbital parameters. To rule out such a possibility would
require (currently unavailable) information about higher-order self-force
corrections.Comment: 13 pages, 3 figure
Setting the cornerstone for the IMRPhenomX family of models for gravitational waves from compact binaries: The dominant harmonic for non-precessing quasi-circular black holes
In this paper we present IMRPhenomXAS, a thorough overhaul of the IMRPhenomD
[1,2] waveform model, which describes the dominant spherical
harmonic mode of non-precessing coalescing black holes in terms of piecewise
closed form expressions in the frequency domain. Improvements include in
particular the accurate treatment of unequal spin effects, and the inclusion of
extreme mass ratio waveforms. IMRPhenomD has previously been extended to
approximately include spin precession [3] and subdominant spherical harmonics
[4], and with its extensions it has become a standard tool in gravitational
wave parameter estimation. Improved extensions of IMRPhenomXAS are discussed in
companion papers [5,6].Comment: 29 pages. 20 figures. Comments and feedback welcome! This paper
corresponds to LIGO DCC P200001
IMRPhenomXHM: A multi-mode frequency-domain model for the gravitational wave signal from non-precessing black-hole binaries
We present the IMRPhenomXHM frequency domain phenomenological waveform model
for the inspiral, merger and ringdown of quasi-circular non-precessing black
hole binaries. The model extends the IMRPhenomXAS waveform model, which
describes the dominant quadrupole modes , to the harmonics
, and includes mode mixing effects for
the spherical harmonic. IMRPhenomXHM is calibrated against hybrid
waveforms, which match an inspiral phase described by the effective-one-body
model and post-Newtonian amplitudes for the subdominant harmonics to numerical
relativity waveforms and numerical solutions to the perturbative Teukolsky
equation for large mass ratios up to 1000.
A computationally efficient implementation of the model is available as part
of the LSC Algorithm Library Suite.Comment: 30 pages, 23 figures. Updated to match published versio
Constraints from LIGO O3 Data on Gravitational-wave Emission Due to R-modes in the Glitching Pulsar PSR J0537-6910
Abbott, R., et al.We present a search for continuous gravitational-wave emission due to r-modes in the pulsar PSR J0537-6910 using data from the LIGO-Virgo Collaboration observing run O3. PSR J0537-6910 is a young energetic X-ray pulsar and is the most frequent glitcher known. The inter-glitch braking index of the pulsar suggests that gravitational-wave emission due to r-mode oscillations may play an important role in the spin evolution of this pulsar. Theoretical models confirm this possibility and predict emission at a level that can be probed by ground-based detectors. In order to explore this scenario, we search for r-mode emission in the epochs between glitches by using a contemporaneous timing ephemeris obtained from NICER data. We do not detect any signals in the theoretically expected band of 86-97 Hz, and report upper limits on the amplitude of the gravitational waves. Our results improve on previous amplitude upper limits from r-modes in J0537-6910 by a factor of up to 3 and place stringent constraints on theoretical models for r-mode-driven spin-down in PSR J0537-6910, especially for higher frequencies at which our results reach below the spin-down limit defined by energy conservation.This work was supported by MEXT, JSPS Leading-edge Research Infrastructure Program, JSPS Grant-in-Aid for Specially Promoted Research 26000005, JSPS Grant-in-Aid for Scientific Research on Innovative Areas 2905: JP17H06358, JP17H06361 and JP17H06364, JSPS Core-to-Core Program A. Advanced Research Networks, JSPS Grant-in-Aid for Scientific Research (S) 17H06133, the joint research program of the Institute for Cosmic Ray Research, University of Tokyo, National Research Foundation (NRF) and Computing Infrastructure Project of KISTI-GSDC in Korea, Academia Sinica (AS), AS Grid Center (ASGC) and the Ministry of Science and Technology (MoST) in Taiwan under grants including AS-CDA-105-M06, Advanced Technology Center (ATC) of NAOJ, and Mechanical Engineering Center of KEK. We would like to thank all of the essential workers who put their health at risk during the COVID-19 pandemic, without whom we would not have been able to complete this work
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