65 research outputs found
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
The Cosmological Probability Density Function for Bianchi Class A Models in Quantum Supergravity
Nicolai's theorem suggests a simple stochastic interpetation for
supersymmetric Euclidean quantum theories, without requiring any inner product
to be defined on the space of states. In order to apply this idea to
supergravity, we first reduce to a one-dimensional theory with local
supersymmetry by the imposition of homogeneity conditions. We then make the
supersymmetry rigid by imposing gauge conditions, and quantise to obtain the
evolution equation for a time-dependent wave function. Owing to the inclusion
of a certain boundary term in the classical action, and a careful treatment of
the initial conditions, the evolution equation has the form of a Fokker-Planck
equation. Of particular interest is the static solution, as this satisfies all
the standard quantum constraints. This is naturally interpreted as a
cosmological probability density function, and is found to coincide with the
square of the magnitude of the conventional wave function for the wormhole
state.Comment: 22 pages, Late
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
The C_2 heat-kernel coefficient in the presence of boundary discontinuities
We consider the heat-kernel on a manifold whose boundary is piecewise smooth.
The set of independent geometrical quantities required to construct an
expression for the contribution of the boundary discontinuities to the C_{2}
heat-kernel coefficient is derived in the case of a scalar field with Dirichlet
and Robin boundary conditions. The coefficient is then determined using
conformal symmetry and evaluation on some specific manifolds. For the Robin
case a perturbation technique is also developed and employed. The contributions
to the smeared heat-kernel coefficient and cocycle function are calculated.
Some incomplete results for spinor fields with mixed conditions are also
presented.Comment: 25 pages, LaTe
Euclidean Black Hole Vortices
We argue the existence of solutions of the Euclidean Einstein equations that
correspond to a vortex sitting at the horizon of a black hole. We find the
asymptotic behaviours, at the horizon and at infinity, of vortex solutions for
the gauge and scalar fields in an abelian Higgs model on a Euclidean
Schwarzschild background and interpolate between them by integrating the
equations numerically. Calculating the backreaction shows that the effect of
the vortex is to cut a slice out of the Euclidean Schwarzschild geometry.
Consequences of these solutions for black hole thermodynamics are discussed.Comment: 24 page
The fate of Reissner-Nortstr\"{o}m black hole in the Einstein-Yang-Mills-Higgs system
We study about an evaporating process of black holes in SO(3)
Einstein-Yang-Mills-Higgs system. We consider a massless scalar field which
couple neither with the Yang-Mills field nor with the Higgs field surrounding
the black hole. We discuss differences in evaporating rate between a monopole
black hole and a Reissner-Nortstr\"{o}m (RN) black hole.Comment: 9 pages, 8 figure
Non-Abelian Black Holes in Brans-Dicke Theory
We find a black hole solution with non-Abelian field in Brans-Dicke theory.
It is an extension of non-Abelian black hole in general relativity. We discuss
two non-Abelian fields: "SU(2)" Yang-Mills field with a mass (Proca field) and
the SU(2)SU(2) Skyrme field. In both cases, as in general relativity,
there are two branches of solutions, i.e., two black hole solutions with the
same horizon radius. Masses of both black holes are always smaller than those
in general relativity. A cusp structure in the mass-horizon radius
(-) diagram, which is a typical symptom of stability change in
catastrophe theory, does not appear in the Brans-Dicke frame but is found in
the Einstein conformal frame. This suggests that catastrophe theory may be
simply applied for a stability analysis as it is if we use the variables in the
Einstein frame. We also discuss the effects of the Brans-Dicke scalar field on
black hole structure.Comment: 31 pages, revtex, 21 figure
Spectral asymptotics of Euclidean quantum gravity with diff-invariant boundary conditions
A general method is known to exist for studying Abelian and non-Abelian gauge
theories, as well as Euclidean quantum gravity, at one-loop level on manifolds
with boundary. In the latter case, boundary conditions on metric perturbations
h can be chosen to be completely invariant under infinitesimal diffeomorphisms,
to preserve the invariance group of the theory and BRST symmetry. In the de
Donder gauge, however, the resulting boundary-value problem for the Laplace
type operator acting on h is known to be self-adjoint but not strongly
elliptic. The latter is a technical condition ensuring that a unique smooth
solution of the boundary-value problem exists, which implies, in turn, that the
global heat-kernel asymptotics yielding one-loop divergences and one-loop
effective action actually exists. The present paper shows that, on the
Euclidean four-ball, only the scalar part of perturbative modes for quantum
gravity are affected by the lack of strong ellipticity. Further evidence for
lack of strong ellipticity, from an analytic point of view, is therefore
obtained. Interestingly, three sectors of the scalar-perturbation problem
remain elliptic, while lack of strong ellipticity is confined to the remaining
fourth sector. The integral representation of the resulting zeta-function
asymptotics is also obtained; this remains regular at the origin by virtue of a
spectral identity here obtained for the first time.Comment: 25 pages, Revtex-4. Misprints in Eqs. (5.11), (5.14), (5.16) have
been correcte
On the absence of scalar hair for charged rotating blackholes in non minimally coupled theories
In this work we check the validity of the no scalar hair theorem in charged
axisymmetric stationary black holes for a wide class of scalar tensor theories.Comment: Revtex style, 11 pages, major rivisions done, appendix added, title
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