785 research outputs found
On the existence of dyons and dyonic black holes in Einstein-Yang-Mills theory
We study dyonic soliton and black hole solutions of the
Einstein-Yang-Mills equations in asymptotically anti-de Sitter space. We prove
the existence of non-trivial dyonic soliton and black hole solutions in a
neighbourhood of the trivial solution. For these solutions the magnetic gauge
field function has no zeros and we conjecture that at least some of these
non-trivial solutions will be stable. The global existence proof uses local
existence results and a non-linear perturbation argument based on the (Banach
space) implicit function theorem.Comment: 23 pages, 2 figures. Minor revisions; references adde
On the stability of soliton and hairy black hole solutions of SU(N) Einstein-Yang-Mills theory with a negative cosmological constant
We investigate the stability of spherically symmetric, purely magnetic, soliton and black hole solutions of four-dimensional su(N) Einstein-Yang-Mills theory with a
negative cosmological constant Î. These solutions are described by N â 1 magnetic gauge field functions Ïj. We consider linear, spherically symmetric, perturbations of these solutions. The perturbations decouple into two sectors, known as the sphaleronic and gravitational sectors. For any N, there are no instabilities in the sphaleronic sector if all the magnetic gauge field functions Ïj have no zeros and satisfy a set of N â 1 inequalities. In the gravitational sector, we prove that there are solutions which have no instabilities in a neighbourhood of stable embedded su(2) solutions, provided the magnitude of the cosmological constant |Î| is sufficiently large.
Kewywords : Stability, hairy black hole, soliton, Einstein-Yang-Mills, anti de-Sitte
Regular and Black Hole Solutions in the Einstein-Skyrme Theory with Negative Cosmological Constant
We study spherically symmetric regular and black hole solutions in the
Einstein-Skyrme theory with a negative cosmological constant. The Skyrme field
configuration depends on the value of the cosmological constant in a similar
manner to effectively varying the gravitational constant. We find the maximum
value of the cosmological constant above which there exists no solution. The
properties of the solutions are discussed in comparison with the asymptotically
flat solutions. The stability is investigated in detail by solving the linearly
perturbed equation numerically. We show that there exists a critical value of
the cosmological constant above which the solution in the branch representing
unstable configuration in the asymptotically flat spacetime turns to be
linearly stable.Comment: 10 pages, 9 figures, comments and one reference added, to appear in
Class.Quant.Gra
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
Do stringy corrections stabilize coloured black holes?
We consider hairy black hole solutions of Einstein-Yang-Mills-Dilaton theory,
coupled to a Gauss-Bonnet curvature term, and we study their stability under
small, spacetime-dependent perturbations. We demonstrate that the stringy
corrections do not remove the sphaleronic instabilities of the coloured black
holes with the number of unstable modes being equal to the number of nodes of
the background gauge function. In the gravitational sector, and in the limit of
an infinitely large horizon, the coloured black holes are also found to be
unstable. Similar behaviour is exhibited by the magnetically charged black
holes while the bulk of the neutral black holes are proven to be stable under
small, gauge-dependent perturbations. Finally, the electrically charged black
holes are found to be characterized only by the existence of a gravitational
sector of perturbations. As in the case of neutral black holes, we demonstrate
that for the bulk of electrically charged black holes no unstable modes arise
in this sector.Comment: 17 pages, Revtex, comments and a reference added, version to appear
in Physical Review
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
Aspects of hairy black holes in spontaneously-broken Einstein-Yang-Mills systems: Stability analysis and Entropy considerations
We analyze (3+1)-dimensional black-hole space-times in spontaneously broken
Yang-Mills gauge theories that have been recently presented as candidates for
an evasion of the scalar-no-hair theorem. Although we show that in principle
the conditions for the no-hair theorem do not apply to this case, however we
prove that the `spirit' of the theorem is not violated, in the sense that there
exist instabilities, in both the sphaleron and gravitational sectors. The
instability analysis of the sphaleron sector, which was expected to be unstable
for topological reasons, is performed by means of a variational method. As
shown, there exist modes in this sector that are unstable against linear
perturbations. Instabilities exist also in the gravitational sector. A method
for counting the gravitational unstable modes, which utilizes a
catastrophe-theoretic approach is presented. The r\^ole of the catastrophe
functional is played by the mass functional of the black hole. The Higgs vacuum
expectation value (v.e.v.) is used as a control parameter, having a critical
value beyond which instabilities are turned on. The (stable) Schwarzschild
solution is then understood from this point of view. The catastrophe-theory
appproach facilitates enormously a universal stability study of non-Abelian
black holes, which goes beyond linearized perturbations. Some elementary
entropy considerations are also presented...Comment: Latex file, 50 pages, 2 figures (included as PS files at the end:
plot1.ps, plot2.ps
Five-dimensional Black Hole and Particle Solution with Non-Abelian Gauge Field
We study the 5-dimensional Einstein-Yang-Mills system with a cosmological
constant. Assuming a spherically symmetric spacetime, we find a new analytic
black hole solution, which approaches asymptotically "quasi-Minkowski", "quasi
anti-de Sitter", or "quasi de Sitter" spacetime depending on the sign of a
cosmological constant. Since there is no singularity except for the origin
which is covered by an event horizon, we regard it as a localized object. This
solution corresponds to a magnetically charged black hole.
We also present a singularity-free particle-like solution and a non-trivial
black hole solution numerically. Those solutions correspond to the
Bartnik-McKinnon solution and a colored black hole with a cosmological constant
in the 4-dimensions. We analyze their asymptotic behaviors, spacetime
structures and thermodynamical properties. We show that there is a set of
stable solutions if a cosmological constant is negative.Comment: 17 pages, 17 figures, submitted to PR
Abelian Higgs Hair for a Static Charged Black String
We study the problem of vortex solutions in the background of an electrically
charged black string. We show numerically that the Abelian Higgs field
equations in the background of a four-dimensional black string have vortex
solutions. These solutions which have axial symmetry, show that the black
string can support the Abelian Higgs field as hair. This situation holds also
in the case of the extremal black string. We also consider the self-gravity of
the Abelian Higgs field and show that the effect of the vortex is to induce a
deficit angle in the metric under consideration.Comment: REVTEX4, 12 pages, 6 figures, The version to be appeared in Phys.
Rev.
Vacuum polarization on the brane
We compute the renormalized expectation value of the square of a massless, conformally coupled, quantum scalar field on the brane of a higher-dimensional black hole. Working in the AADD brane-world scenario, the extra dimensions are flat and we assume that the compactification radius is large compared with the size of the black hole. The four-dimensional on-brane metric corresponds to a slice through a higher-dimensional Schwarzschild-Tangherlini black hole geometry and depends on the number of bulk space-time dimensions. The quantum scalar field is in a thermal state at the Hawking temperature. An exact, closed-form expression is derived for the renormalized expectation value of the square of the quantum scalar field on the event horizon of the black hole. Outside the event horizon, this renormalized expectation value is computed numerically. The answer depends on the number of bulk space-time dimensions, with a magnitude which increases rapidly as the number of bulk space-time dimensions increases
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