7,111 research outputs found
Topological geon black holes in Einstein-Yang-Mills theory
We construct topological geon quotients of two families of
Einstein-Yang-Mills black holes. For Kuenzle's static, spherically symmetric
SU(n) black holes with n>2, a geon quotient exists but generically requires
promoting charge conjugation into a gauge symmetry. For Kleihaus and Kunz's
static, axially symmetric SU(2) black holes a geon quotient exists without
gauging charge conjugation, and the parity of the gauge field winding number
determines whether the geon gauge bundle is trivial. The geon's gauge bundle
structure is expected to have an imprint in the Hawking-Unruh effect for
quantum fields that couple to the background gauge field.Comment: 27 pages. v3: Presentation expanded. Minor corrections and addition
Searchable Sky Coverage of Astronomical Observations: Footprints and Exposures
Sky coverage is one of the most important pieces of information about
astronomical observations. We discuss possible representations, and present
algorithms to create and manipulate shapes consisting of generalized spherical
polygons with arbitrary complexity and size on the celestial sphere. This shape
specification integrates well with our Hierarchical Triangular Mesh indexing
toolbox, whose performance and capabilities are enhanced by the advanced
features presented here. Our portable implementation of the relevant spherical
geometry routines comes with wrapper functions for database queries, which are
currently being used within several scientific catalog archives including the
Sloan Digital Sky Survey, the Galaxy Evolution Explorer and the Hubble Legacy
Archive projects as well as the Footprint Service of the Virtual Observatory.Comment: 11 pages, 7 figures, submitted to PAS
Action and Hamiltonian for eternal black holes
We present the Hamiltonian, quasilocal energy, and angular momentum for a
spacetime region spatially bounded by two timelike surfaces. The results are
applied to the particular case of a spacetime representing an eternal black
hole. It is shown that in the case when the boundaries are located in two
different wedges of the Kruskal diagram, the Hamiltonian is of the form , where and are the Hamiltonian functions for the right
and left wedges respectively. The application of the obtained results to the
thermofield dynamics description of quantum effects in black holes is briefly
discussed.Comment: 24 pages, Revtex, 5 figures (available upon request
Supergravity p-branes revisited: extra parameters, uniqueness, and topological censorship
We perform a complete integration of the Einstein-dilaton-antisymmetric form
action describing black p-branes in arbitrary dimensions assuming the
transverse space to be homogeneous and possessing spherical, toroidal or
hyperbolic topology. The generic solution contains eight parameters satisfying
one constraint. Asymptotically flat solutions form a five-parametric subspace,
while conditions of regularity of the non-degenerate event horizon further
restrict this number to three, which can be related to the mass and the charge
densities and the asymptotic value of the dilaton. In the case of a degenerate
horizon, this number is reduced by one. Our derivation constitutes a
constructive proof of the uniqueness theorem for -branes with the
homogeneous transverse space. No asymptotically flat solutions with toroidal or
hyperbolic transverse space within the considered class are shown to exist,
which result can be viewed as a demonstration of the topological censorship for
p-branes. From our considerations it follows, in particular, that some
previously discussed p-brane-like solutions with extra parameters do not
satisfy the standard conditions of asymptotic flatness and absence of naked
singularities. We also explore the same system in presence of a cosmological
constant, and derive a complete analytic solution for higher-dimensional
charged topological black holes, thus proving their uniqueness.Comment: Revtex4, no figure
High Q BPS Monopole Bags are Urchins
It has been known for 30 years that 't Hooft-Polyakov monopoles of charge Q
greater than one cannot be spherically symmetric. 5 years ago, Bolognesi
conjectured that, at some point in their moduli space, BPS monopoles can become
approximately spherically symmetric in the high Q limit. In this note we
determine the sense in which this conjecture is correct. We consider an SU(2)
gauge theory with an adjoint scalar field, and numerically find configurations
with Q units of magnetic charge and a mass which is roughly linear in Q, for
example in the case Q=81 we present a configuration whose energy exceeds the
BPS bound by about 54 percent. These approximate solutions are constructed by
gluing together Q cones, each of which contains a single unit of magnetic
charge. In each cone, the energy is largest in the core, and so a constant
energy density surface contains Q peaks and thus resembles a sea urchin. We
comment on some relations between a non-BPS cousin of these solutions and the
dark matter halos of dwarf spherical galaxies.Comment: LaTeX, 25 pages, 4 figure
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