11,090 research outputs found
Bohm and Einstein-Sasaki Metrics, Black Holes and Cosmological Event Horizons
We study physical applications of the Bohm metrics, which are infinite
sequences of inhomogeneous Einstein metrics on spheres and products of spheres
of dimension 5 <= d <= 9. We prove that all the Bohm metrics on S^3 x S^2 and
S^3 x S^3 have negative eigenvalue modes of the Lichnerowicz operator and by
numerical methods we establish that Bohm metrics on S^5 have negative
eigenvalues too. We argue that all the Bohm metrics will have negative modes.
These results imply that higher-dimensional black-hole spacetimes where the
Bohm metric replaces the usual round sphere metric are classically unstable. We
also show that the stability criterion for Freund-Rubin solutions is the same
as for black-hole stability, and hence such solutions using Bohm metrics will
also be unstable. We consider possible endpoints of the instabilities, and show
that all Einstein-Sasaki manifolds give stable solutions. We show how Wick
rotation of Bohm metrics gives spacetimes that provide counterexamples to a
strict form of the Cosmic Baldness conjecture, but they are still consistent
with the intuition behind the cosmic No-Hair conjectures. We show how the
Lorentzian metrics may be created ``from nothing'' in a no-boundary setting. We
argue that Lorentzian Bohm metrics are unstable to decay to de Sitter
spacetime. We also argue that noncompact versions of the Bohm metrics have
infinitely many negative Lichernowicz modes, and we conjecture a general
relation between Lichnerowicz eigenvalues and non-uniqueness of the Dirichlet
problem for Einstein's equations.Comment: 53 pages, 11 figure
Isometric Embedding of BPS Branes in Flat Spaces with Two Times
We show how non-near horizon p-brane theories can be obtained from two
embedding constraints in a flat higher dimensional space with 2 time
directions. In particular this includes the construction of D3 branes from a
flat 12-dimensional action, and M2 and M5 branes from 13 dimensions. The
worldvolume actions are determined by constant forms in the higher dimension,
reduced to the usual expressions by Lagrange multipliers. The formulation
affords insight in the global aspects of the spacetime geometries and makes
contact with recent work on two-time physics.Comment: 29 pages, 10 figures, Latex using epsf.sty and here.sty; v2:
reference added and some small correction
Charged Dilaton Black Holes with a Cosmological Constant
The properties of static spherically symmetric black holes, which are either
electrically or magnetically charged, and which are coupled to the dilaton in
the presence of a cosmological constant, are considered. It is shown that such
solutions do not exist if the cosmological constant is positive (in arbitrary
spacetime dimension >= 4). However, asymptotically anti-de Sitter black hole
solutions with a single horizon do exist if the cosmological constant is
negative. These solutions are studied numerically in four dimensions and the
thermodynamic properties of the solutions are derived. The extreme solutions
are found to have zero entropy and infinite temperature for all non-zero values
of the dilaton coupling constant.Comment: 12 pages, epsf, phyzzx, 4 in-text figures incl. (minor typos fixed, 1
reference added
Uniqueness and non-uniqueness of static vacuum black holes in higher dimensions
We prove the uniqueness theorem for asymptotically flat static vacuum black
hole solutions in higher dimensional space-times. We also construct infinitely
many non-asymptotically flat regular static black holes on the same spacetime
manifold with the same spherical topology.Comment: to appear in Progress of Theoretical Physics Supplement No. 14
Exponentially Large Probabilities in Quantum Gravity
The problem of topology change transitions in quantum gravity is investigated
from the Wheeler-de Witt wave function point of view. It is argued that for all
theories allowing wormhole effects the wave function of the universe is
exponentially large. If the wormhole action is positive, one can try to
overcome this difficulty by redefinition of the inner product, while for the
case of negative wormhole action the more serious problems arise.Comment: 9 pages in LaTeX, 4 figures in PostScript, the brief version of this
paper is to appear in Proceedings of the XXIV ITEP Winter School of Physic
The scalar perturbation of the higher-dimensional rotating black holes
The massless scalar field in the higher-dimensional Kerr black hole (Myers-
Perry solution with a single rotation axis) has been investigated. It has been
shown that the field equation is separable in arbitrary dimensions. The
quasi-normal modes of the scalar field have been searched in five dimensions
using the continued fraction method. The numerical result shows the evidence
for the stability of the scalar perturbation of the five-dimensional Kerr black
holes. The time scale of the resonant oscillation in the rapidly rotating black
hole, in which case the horizon radius becomes small, is characterized by
(black hole mass)^{1/2}(Planck mass)^{-3/2} rather than the light-crossing time
of the horizon.Comment: 16 pages, 7 figures, revised versio
Evolution of a Self-interacting Scalar Field in the spacetime of a Higher Dimensional Black Hole
In the spacetime of n-dimensional static charged black hole we examine the
mechanism by which the self-interacting scalar hair decay. It is turned out
that the intermediate asymptotic behaviour of the self-interacting scalar field
is determined by an oscilatory inverse power law. We confirm our results by
numerical calculations.Comment: RevTex, 6 pages, 8 figures, to be published in Phys.Rev.D1
Nucleating Black Holes via Non-Orientable Instantons
We extend the analysis of black hole pair creation to include non- orientable
instantons. We classify these instantons in terms of their fundamental
symmetries and orientations. Many of these instantons admit the pin structure
which corresponds to the fermions actually observed in nature, and so the
natural objection that these manifolds do not admit spin structure may not be
relevant. Furthermore, we analyse the thermodynamical properties of
non-orientable black holes and find that in the non-extreme case, there are
interesting modifications of the usual formulae for temperature and entropy.Comment: 27 pages LaTeX, minor typos are correcte
Dyonic dilaton black holes
The properties of static spherically symmetric black holes, which are both
electrically and magnetically charged, and which are coupled to the dilaton in
the presence of a cosmological constant, Lambda, are considered. It is shown
that apart from the Reissner-Nordstrom-de Sitter solution with constant
dilaton, such solutions do not exist if Lambda > 0 (in arbitrary spacetime
dimension >=4 ). However, asymptotically anti-de Sitter dyonic black hole
solutions with a non-trivial dilaton do exist if Lambda < 0. Both these
solutions and the asymptotically flat (Lambda = 0) solutions are studied
numerically for arbitrary values of the dilaton coupling parameter, g_0, in
four dimensions. The asymptotically flat solutions are found to exhibit two
horizons if g_0 = 0, 1, \sqrt{3}, \sqrt{6}, ..., \sqrt{n(n+1)/2},..., and one
horizon otherwise. For asymptotically anti-de Sitter solutions the result is
similar, but the corresponding values of g_0 are altered in a non-linear
fashion which depends on Lambda and the mass and charges of the black holes.
All dyonic solutions with Lambda <= 0 are found to have zero Hawking
temperature in the extreme limit, however, regardless of the value of g_0.Comment: 24 pages, phyzzx, epsf, 7 in-text figures. Small addition to
introduction, and a few extra reference
- …