569 research outputs found
Abundant stable gauge field hair for black holes in anti-de sitter space
We present new hairy black hole solutions of SU(N) Einstein-Yang-Mills (EYM) theory in asymptotically antiâde Sitter (AdS) space. These black holes are described by N+1 independent parameters and have N-1 independent gauge field degrees of freedom. Solutions in which all gauge field functions have no zeros exist for all N, and for a sufficiently large (and negative) cosmological constant. At least some of these solutions are shown to be stable under classical, linear, spherically symmetric perturbations. Therefore there is no upper bound on the amount of stable gauge field hair with which a black hole in AdS can be endowed
Monograph No. 13: Scoping the potential uses of systems thinking in developing policy on illcit drugs
This monograph (No. 13) summarises pilot work to scope the potential uses of systems thinking for developing illicit drug policy. Systems approaches have the potential to offer much to drug policy analysis through their use of participatory methods, capacity to deal with multiple simultaneous policy options, and appreciation of the complexity, interconnectedness and dynamic feedback loops associated with policy decisions. The monograph outlines six systems approaches used by the New Zealand team in exploring illicit drug policy. The results of in-depth interviews with five experienced policy makers and a demonstration project around a policy issue are described. The potential utility of systems approaches in illicit drug policy are demonstrated
Bulletin No. 9: Scoping the potential uses of systems thinking in developing policy on illicit drugs
While a great variety of systems approaches have
been developed, they all have some common
characteristics: a recognition of the need to deal
with complex issues by looking at the âbigger
pictureâ; the evaluation of multiple policy options
prior to (and often during and after)
implementation; and exploring interconnections
and potential consequences to identify and
minimise unwanted âside-effectsâ of policy. While
this focus of systems thinking on dealing with
complexity has been found to be useful in many
other policy contexts, such as policing and
sustainable cities, systems approaches have been
used less frequently in policy making on illicit
drugs. However, given that this area of policy can
be highly complex, characterised by tensions
between stakeholder groups and requiring difficult
balances to be struck between enforcement,
prevention and treatment, it seems worthwhile to
explore what added value systems approaches can
offer, and what barriers to their use might be
encountered. This DPMP project was designed to
scope the potential uses of systems thinking for
developing policy on illicit drugs
Geon black holes and quantum field theory
Black hole spacetimes that are topological geons in the sense of Sorkin can
be constructed by taking a quotient of a stationary black hole that has a
bifurcate Killing horizon. We discuss the geometric properties of these geon
black holes and the Hawking-Unruh effect on them. We in particular show how
correlations in the Hawking-Unruh effect reveal to an exterior observer
features of the geometry that are classically confined to the regions behind
the horizons.Comment: 11 pages. Talk given at the First Mediterranean Conference on
Classical and Quantum Gravity, Kolymbari (Crete, Greece), September 2009.
Dedicated to Rafael Sorkin. v2: typesetting bug fixe
Soliton and black hole solutions of su(N) Einstein-Yang-Mills theory in anti-de Sitter space
We present new soliton and hairy black hole solutions of su(N)
Einstein-Yang-Mills theory in asymptotically anti-de Sitter space. These
solutions are described by N+1 independent parameters, and have N-1 gauge field
degrees of freedom. We examine the space of solutions in detail for su(3) and
su(4) solitons and black holes. If the magnitude of the cosmological constant
is sufficiently large, we find solutions where all the gauge field functions
have no zeros. These solutions are of particular interest because we anticipate
that at least some of them will be linearly stable.Comment: 15 pages, 20 figures, minor changes, accepted for publication in
Physical Review
On the linear stability of solitons and hairy black holes with a negative cosmological constant: the odd-parity sector
Using a recently developed perturbation formalism based on curvature
quantities, we investigate the linear stability of black holes and solitons
with Yang-Mills hair and a negative cosmological constant. We show that those
solutions which have no linear instabilities under odd- and even- parity
spherically symmetric perturbations remain stable under odd-parity, linear,
non-spherically symmetric perturbations.Comment: 26 pages, 1 figur
Gravitating sphalerons and sphaleron black holes in asymptotically anti-de Sitter spacetime
Numerical arguments are presented for the existence of spherically symmetric
regular and black hole solutions of the EYMH equations with a negative
cosmological constant. These solutions approach asymptotically the anti-de
Sitter spacetime. The main properties of the solutions and the differences with
respect to the asymptotically flat case are discussed. The instability of the
gravitating sphaleron solutions is also proven.Comment: 30 pages, LaTeX, 8 Encapsulated PostScript figure
New hairy black hole solutions with a dilaton potential
We consider black hole solutions with a dilaton field possessing a nontrivial
potential approaching a constant negative value at infinity. The asymptotic
behaviour of the dilaton field is assumed to be slower than that of a localized
distribution of matter. A nonabelian SU(2) gauge field is also included in the
total action. The mass of the solutions admitting a power series expansion in
at infinity and preserving the asymptotic anti-de Sitter geometry is
computed by using a counterterm subtraction method. Numerical arguments are
presented for the existence of hairy black hole solutions for a dilaton
potential of the form , special attention being paid to the case of
gauged supergravity model of Gates and Zwiebach.Comment: 12 pages, 4 figures; v2:references added, typos corrected, small
changes in Section
Vacuum polarization for lukewarm black holes
We compute the renormalized expectation value of the square of a quantum scalar field on a Reissner-Nordströmâde Sitter black hole in which the temperatures of the event and cosmological horizons are equal (âlukewarmâ black hole). Our numerical calculations for a thermal state at the same temperature as the two horizons indicate that this renormalized expectation value is regular on both the event and cosmological horizons. We are able to show analytically, using an approximation for the field modes near the horizons, that this is indeed the case
Static axially symmetric solutions of Einstein-Yang-Mills equations with a negative cosmological constant: black hole solutions
We investigate static axially symmetric black hole solutions in a
four-dimensional Einstein-Yang-Mills-SU(2) theory with a negative cosmological
constant . These solutions approach asymptotically the anti-de Sitter
spacetime and possess a regular event horizon. A discussion of the main
properties of the solutions and the differences with respect to the
asymptotically flat case is presented. The mass of these configurations is
computed by using a counterterm method. We note that the
configurations have an higher dimensional interpretation in context of
supergravity. The existence of axially symmetric monopole and dyon solutions in
a fixed Schwarzschild-anti-de Sitter background is also discussed. An exact
solution of the Einstein-Yang-Mills equations is presented in Appendix.Comment: 47 pages, 47 figure
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