1,269 research outputs found
On Hawking's Local Rigidity Theorems for Charged Black Holes
We show the existence of a Hawking vector field in a full neighborhood of a
local, regular, bifurcate, non-expanding horizon embedded in a smooth
Einstein-Maxwell space-time without assuming the underlying space-time is
analytic. It extends one result of Friedrich, R\'{a}cz and Wald, which was
limited to the interior of the black hole region. Moreover, we also show, in
the presence of an additional Killing vector field which tangent to the
horizon and not vanishing on the bifurcate sphere, then space-time must be
locally axially symmetric without the analyticity assumption. This axial
symmetry plays a fundamental role in the classification theory of stationary
black holes.Comment: 20 page
A black ring with a rotating 2-sphere
We present a solution of the vacuum Einstein's equations in five dimensions
corresponding to a black ring with horizon topology S^1 x S^2 and rotation in
the azimuthal direction of the S^2. This solution has a regular horizon up to a
conical singularity, which can be placed either inside the ring or at infinity.
This singularity arises due to the fact that this black ring is not balanced.
In the infinite radius limit we correctly reproduce the Kerr black string, and
taking another limit we recover the Myers-Perry black hole with a single
angular momentum.Comment: 10 page
Towards a formalism for mapping the spacetimes of massive compact objects: Bumpy black holes and their orbits
Observations have established that extremely compact, massive objects are
common in the universe. It is generally accepted that these objects are black
holes. As observations improve, it becomes possible to test this hypothesis in
ever greater detail. In particular, it is or will be possible to measure the
properties of orbits deep in the strong field of a black hole candidate (using
x-ray timing or with gravitational-waves) and to test whether they have the
characteristics of black hole orbits in general relativity. Such measurements
can be used to map the spacetime of a massive compact object, testing whether
the object's multipoles satisfy the strict constraints of the black hole
hypothesis. Such a test requires that we compare against objects with the
``wrong'' multipole structure. In this paper, we present tools for constructing
bumpy black holes: objects that are almost black holes, but that have some
multipoles with the wrong value. The spacetimes which we present are good deep
into the strong field of the object -- we do not use a large r expansion,
except to make contact with weak field intuition. Also, our spacetimes reduce
to the black hole spacetimes of general relativity when the ``bumpiness'' is
set to zero. We propose bumpy black holes as the foundation for a null
experiment: if black hole candidates are the black holes of general relativity,
their bumpiness should be zero. By comparing orbits in a bumpy spacetime with
those of an astrophysical source, observations should be able to test this
hypothesis, stringently testing whether they are the black holes of general
relativity. (Abridged)Comment: 16 pages + 2 appendices + 3 figures. Submitted to PR
Rotating Einstein-Yang-Mills Black Holes
We construct rotating hairy black holes in SU(2) Einstein-Yang-Mills theory.
These stationary axially symmetric black holes are asymptotically flat. They
possess non-trivial non-Abelian gauge fields outside their regular event
horizon, and they carry non-Abelian electric charge. In the limit of vanishing
angular momentum, they emerge from the neutral static spherically symmetric
Einstein-Yang-Mills black holes, labelled by the node number of the gauge field
function. With increasing angular momentum and mass, the non-Abelian electric
charge of the solutions increases, but remains finite. The asymptotic expansion
for these black hole solutions includes non-integer powers of the radial
variable.Comment: 63 pages, 10 figure
Periodic Orbits and Escapes in Dynamical Systems
We study the periodic orbits and the escapes in two different dynamical
systems, namely (1) a classical system of two coupled oscillators, and (2) the
Manko-Novikov metric (1992) which is a perturbation of the Kerr metric (a
general relativistic system). We find their simple periodic orbits, their
characteristics and their stability. Then we find their ordered and chaotic
domains. As the energy goes beyond the escape energy, most chaotic orbits
escape. In the first case we consider escapes to infinity, while in the second
case we emphasize escapes to the central "bumpy" black hole. When the energy
reaches its escape value a particular family of periodic orbits reaches an
infinite period and then the family disappears (the orbit escapes). As this
family approaches termination it undergoes an infinity of equal period and
double period bifurcations at transitions from stability to instability and
vice versa. The bifurcating families continue to exist beyond the escape
energy. We study the forms of the phase space for various energies, and the
statistics of the chaotic and escaping orbits. The proportion of these orbits
increases abruptly as the energy goes beyond the escape energy.Comment: 28 pages, 23 figures, accepted in "Celestial Mechanics and Dynamical
Astronomy
Five Dimensional Rotating Black Hole in a Uniform Magnetic Field. The Gyromagnetic Ratio
In four dimensional general relativity, the fact that a Killing vector in a
vacuum spacetime serves as a vector potential for a test Maxwell field provides
one with an elegant way of describing the behaviour of electromagnetic fields
near a rotating Kerr black hole immersed in a uniform magnetic field. We use a
similar approach to examine the case of a five dimensional rotating black hole
placed in a uniform magnetic field of configuration with bi-azimuthal symmetry,
that is aligned with the angular momenta of the Myers-Perry spacetime. Assuming
that the black hole may also possess a small electric charge we construct the
5-vector potential of the electromagnetic field in the Myers-Perry metric using
its three commuting Killing vector fields. We show that, like its four
dimensional counterparts, the five dimensional Myers-Perry black hole rotating
in a uniform magnetic field produces an inductive potential difference between
the event horizon and an infinitely distant surface. This potential difference
is determined by a superposition of two independent Coulomb fields consistent
with the two angular momenta of the black hole and two nonvanishing components
of the magnetic field. We also show that a weakly charged rotating black hole
in five dimensions possesses two independent magnetic dipole moments specified
in terms of its electric charge, mass, and angular momentum parameters. We
prove that a five dimensional weakly charged Myers-Perry black hole must have
the value of the gyromagnetic ratio g=3.Comment: 23 pages, REVTEX, v2: Minor changes, v3: Minor change
Molluscs of the Natural Well Locality, Duplin Stratotype, Near Magnolia, North Carolina, and Rediscovery of Carinorbis Quadricostata (Emmons, 1858) (Gastopoda: Amathinidae)
The Duplin Formation stratotype at the Natural Well limestone sink near Magnolia, North Carolina, is commonly thought to be the source of one of the most thoroughly documented Pliocene molluscan faunas in the Carolinas. However, few of the 196 species listed by Dall (1903) as from "the Duplin well or the adjacent village of Magnolia" were actually collected from Natural Well. Neither the coding of Dall\u27s lists nor reference in text clearly indicates which specimens were collected from the stratotype section. A stratigraphically pure Natural Well collection, housed in the Geology Department of the University of North Carolina at Chapel Hill, contains 239 molluscan species (Appendix I). The faunule is low in endemics and high in first appearances of species that continue into the younger Waccamaw faunas . Like the correlative Tearcoat Branch and Muldrow Place faunules the Natural Well faunule contains only a single pectinid species, the ubiquitous Carolinapecten eboreus. The UNC-CH collections contain a number of rare and u nusual species, including a single specimen of Carinorbis quadricostata (Emmons, 1858). This is only the third recorded specimen of this rare and endemic species, and the first that permits comparative systematic analysis. The genus Carinorbis has been overlooked or inaccurately synonymized in most literature
On the `Stationary Implies Axisymmetric' Theorem for Extremal Black Holes in Higher Dimensions
All known stationary black hole solutions in higher dimensions possess
additional rotational symmetries in addition to the stationary Killing field.
Also, for all known stationary solutions, the event horizon is a Killing
horizon, and the surface gravity is constant. In the case of non-degenerate
horizons (non-extremal black holes), a general theorem was previously
established [gr-qc/0605106] proving that these statements are in fact generally
true under the assumption that the spacetime is analytic, and that the metric
satisfies Einstein's equation. Here, we extend the analysis to the case of
degenerate (extremal) black holes. It is shown that the theorem still holds
true if the vector of angular velocities of the horizon satisfies a certain
"diophantine condition," which holds except for a set of measure zero.Comment: 30pp, Latex, no figure
A Higher Dimensional Stationary Rotating Black Hole Must be Axisymmetric
A key result in the proof of black hole uniqueness in 4-dimensions is that a
stationary black hole that is ``rotating''--i.e., is such that the stationary
Killing field is not everywhere normal to the horizon--must be axisymmetric.
The proof of this result in 4-dimensions relies on the fact that the orbits of
the stationary Killing field on the horizon have the property that they must
return to the same null geodesic generator of the horizon after a certain
period, . This latter property follows, in turn, from the fact that the
cross-sections of the horizon are two-dimensional spheres. However, in
spacetimes of dimension greater than 4, it is no longer true that the orbits of
the stationary Killing field on the horizon must return to the same null
geodesic generator. In this paper, we prove that, nevertheless, a higher
dimensional stationary black hole that is rotating must be axisymmetric. No
assumptions are made concerning the topology of the horizon cross-sections
other than that they are compact. However, we assume that the horizon is
non-degenerate and, as in the 4-dimensional proof, that the spacetime is
analytic.Comment: 24 pages, no figures, v2: footnotes and references added, v3:
numerous minor revision
Search for CP Violation in Charged D Meson Decays
We report results of a search for CP violation in the singly
Cabibbo-suppressed decays D+ -> K- K+ pi+, phi pi+, K*(892)0 K+, and pi- pi+
pi+ based on data from the charm hadroproduction experiment E791 at Fermilab.
We search for a difference in the D+ and D- decay rates for each of the final
states. No evidence for a difference is seen. The decay rate asymmetry
parameters A(CP), defined as the difference in the D+ and D- decay rates
divided by the sum of the decay rates, are measured to be: A(CP)(K K pi) =
-0.014 +/- 0.029, A(CP)(phi pi) = -0.028 +/- 0.036, A(CP)(K*(892) K) = -0.010
+/- 0.050, and A(CP)(pi pi pi) = -0.017 +/- 0.042.Comment: 13 pages, 5 figures, 1 table; Elsevier LaTe
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