1,307 research outputs found
On the distribution of stellar-sized black hole spins
Black hole spin will have a large impact on searches for gravitational waves
with advanced detectors. While only a few stellar mass black hole spins have
been measured using X-ray techniques, gravitational wave detectors have the
capacity to greatly increase the statistics of black hole spin measurements. We
show what we might learn from these measurements and how the black hole spin
values are influenced by their formation channels.Comment: 4 pages, 2 figures, pre-GW150914 detection, refereed and accepted
contribution to proceedings of 11th Edoardo Amaldi Conference on
Gravitational Waves, June 2015, Gwangju, Kore
Black holes without boundaries
We discuss some of the drawbacks of using event horizons to define black
holes and suggest ways in which black holes can be described without event
horizons, using trapping horizons. We show that these trapping horizons give
rise to thermodynamic behavior and possibly Hawking radiation too. This raises
the issue of whether the event horizon or the trapping horizon should be seen
as the true boundary of a black hole. This difference is important if we
believe that quantum gravity will resolve the central singularity of the black
hole and clarifies several of the issues associated with black hole
thermodynamics and information loss.Comment: 8 pages. Invited essay for special edition of the International
Journal of Modern Physics
Black Holes without Event Horizons
We discuss some of the drawbacks of using event horizons to define black
holes. The reasons are both practical, physical and theoretical. We argue that
locally defined trapping horizons can remedy many of these drawbacks. We
examine of the question of whether black hole thermodynamics should be
associated with event horizons or trapping horizons. To this end we discuss
what role trapping horizons may play in black hole thermodynamics. In addition,
we show how trapping horizons may give rise to Hawking radiation and discuss
the issue of gravitational entropy.Comment: Talk at APCTP Winter School, Daejeon, Korea, 2008. 7 pages, no
figure
Non-minimally coupled multi-scalar black holes
We study the static, spherically symmetric black hole solutions for a
non-minimally coupled multi-scalar theory. We find numerical solutions for
values of the scalar fields when a certain constraint on the maximal charge is
satisfied. Beyond this constraint no black hole solutions exist. This
constraint therefore corresponds to extremal solutions, however, this does not
match the \kappa = 0 constraint which typically indicates extremal solutions in
other models. This implies that the set of extremal solutions have non-zero,
finite and varying surface gravity. These solutions also violate the no-hair
theorems for N>1 scalar fields and have previously been proven to be linearly
stable.Comment: 6 pages, 4 figure
The slicing dependence of non-spherically symmetric quasi-local horizons in Vaidya Spacetimes
It is well known that quasi-local black hole horizons depend on the choice of
a time coordinate in a spacetime. This has implications for notions such as the
surface of the black hole and also on quasi-local physical quantities such as
horizon measures of mass and angular momentum. In this paper, we compare
different horizons on non-spherically symmetric slicings of Vaidya spacetimes.
The spacetimes we investigate include both accreting and evaporating black
holes. For some simple choices of the Vaidya mass function function
corresponding to collapse of a hollow shell, we compare the area for the
numerically found axisymmetric trapping horizons with the area of the
spherically symmetric trapping horizon and event horizon. We find that as
expected, both the location and area are dependent on the choice of foliation.
However, the area variation is not large, of order for a slowly
evolving horizon with . We also calculate analytically the
difference in area between the spherically symmetric quasi-local horizon and
event horizon for a slowly accreting black hole. We find that the difference
can be many orders of magnitude larger than the Planck area for sufficiently
large black holes.Comment: 10 pages, 5 figures, corrected minor typo
Skyrme Black Holes in the Isolated Horizons Formalism
We study static, spherically symmetric, Skyrme black holes in the context of
the assumption that they can be viewed as bound states between ordinary bare
black holes and solitons. This assumption and results stemming from the
isolated horizons formalism lead to several conjectures about the static black
hole solutions. These conjectures are tested against the Skyrme black hole
solutions. It is shown that, while there is in general good agreement with the
conjectures, a crucial aspect seems to violate one of the conjectures.Comment: Full journal version, 6 pages, 5 figure
Advanced LIGO's ability to detect apparent violations of the cosmic censorship conjecture and the no-hair theorem through compact binary coalescence detections
We study the ability of the advanced Laser Interferometer Gravitational-wave
Observatory (aLIGO) to detect apparent violations of the cosmic censorship
conjecture and the no-hair theorem. The cosmic censorship conjecture, which is
believed to be true in the theory of general relativity, limits the
spin-to-mass-squared ratio of a Kerr black hole. The no-hair theorem, which is
also believed to be true in the theory of general relativity, suggests a
particular value for the tidal Love number of a non-rotating black hole. Using
the Fisher matrix formalism, we examine the measurability of the spin and tidal
deformability of compact binary systems involving at least one putative black
hole. Using parameter measurement errors and correlations obtained from the
Fisher matrix, we determine the smallest detectable violation of bounds implied
by the cosmic censorship conjecture and the no-hair theorem. We examine the
effect of excluding unphysical areas of parameter space when determining the
smallest detectable apparent violations, and we examine the effect of different
post-Newtonian corrections to the amplitude of the compact binary coalescence
gravitational waveform. In addition, we perform a brief study of how the
recently calculated 3.0 pN and 3.5 pN spin-orbit corrections to the phase
affect spin and mass parameter measurability. We find that physical priors on
the symmetric mass ratio and higher harmonics in the gravitational waveform
could significantly affect the ability of aLIGO to investigate cosmic
censorship and the no-hair theorem for certain systems.Comment: 21 pages, 7 figures, 6 table
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