54 research outputs found
Canonical quantization and black hole perturbations
We examine the possibility of a constraint-free quantization of linearized
gravity, based on the Teukolsky equation for black hole perturbations. We
exhibit a simple quadratic (but complex) Lagrangian for the Teukolsky equation,
leading to the interpretation that the elementary excitations (gravitons bound
to the Kerr black hole) are unstable.Comment: Contribution to the XIXth Max Born Symposium, Wroclaw. 10 pages,
LaTeX, no figure
Solutions of the Regge Equations on some Triangulations of CP^2
Simplicial geometries are collections of simplices making up a manifold
together with an assignment of lengths to the edges that define a metric on
that manifold. The simplicial analogs of the Einstein equations are the Regge
equations. Solutions to these equations define the semiclassical approximation
to simplicial approximations to a sum-over-geometries in quantum gravity. In
this paper, we consider solutions to the Regge equations with cosmological
constant that give Euclidean metrics of high symmetry on a family of
triangulations of CP^2 presented by Banchoff and Kuhnel. This family is
characterized by a parameter p. The number of vertices grows larger with
increasing p. We exhibit a solution of the Regge equations for p=2 but find no
solutions for p=3. This example shows that merely increasing the number of
vertices does not ensure a steady approach to a continuum geometry in the Regge
calculus.Comment: 11 pages, uuencoded revtex w/ embedded ps figure. Replaces a
submission which had corrupted ps fil
Generalized Supersymmetries and Composite Structure in M-Theory
We describe generalized D=11 Poincar\'{e} and conformal supersymmetries. The
corresponding generalization of twistor and supertwistor framework is outlined
with superspinors describing BPS preons. The BPS
states as composed out of preons are introduced, and basic ideas
concerning BPS preon dynamics is presented. The lecture is based on results
obtained by J.A. de Azcarraga, I. Bandos, J.M. Izquierdo and the author.Comment: LaTeX, 7pages. Talk presented at the XVI-th Max Born Symposium
,,Supersymmetries and Quantum Symmetries `01" (21-25.09.2001, Karpacz,
Poland) and International Nankai Symposium (8-11.10.2001, Tianjin, China). To
be published in the Proceedings of Nankai Symposium, Ed. Ge Mo-Lin and J.
Park, Int. J. Mod. Phys.
Quaternionic and Hyper-K\"ahler Metrics from Generalized Sigma Models
The problem of finding new metrics of interest, in the context of SUGRA, is
reduced to two stages: first, solving a generalized BPS sigma model with full
quaternionic structure proposed by the authors and, second, constructing the
hyper-K\"{a}hler metric, or suitable deformations of this condition, taking
advantage of the correspondence between the quaternionic left-regular potential
and the hyper-K\"{a}hler metric of the target space. As illustration, new
solutions are obtained using generalized Q-sigma model for Wess-Zumino type
superpotentials. Explicit solutions analog to the Berger's sphere and
Abraham-Townsend type are given and generalizations of 4-dimensional
quaternionic metrics, product of complex ones, are shown and discussed.Comment: 8 pages, two column, no figure
Two-Component Dust in Spherically Symmetric Motion
Two components of spherically symmetric, inhomogeneous dust penetrating each
other are introduced as a generalization of the well-known Tolman-Bondi dust
solution. The field equations of this model are formulated and general
properties are discussed. inhomogeneous Special solutions with additional
symmetries - an extra Killing- or homothetic vector - and their matching to the
corresponding Tolman-Bondi solution are investigated.Comment: 16 pages, LaTeX, 5 figures, accepted for publication in Class.
Quantum Gra
Charged black holes: Wave equations for gravitational and electromagnetic perturbations
A pair of wave equations for the electromagnetic and gravitational
perturbations of the charged Kerr black hole are derived. The perturbed
Einstein-Maxwell equations in a new gauge are employed in the derivation. The
wave equations refer to the perturbed Maxwell spinor and to the shear
of a principal null direction of the Weyl curvature. The whole
construction rests on the tripod of three distinct derivatives of the first
curvature of a principal null direction.Comment: 12 pages, to appear in Ap.
Stringy Probe Particle and Force Balance
We directly derive the classical equation of motion, which governs the centre
of mass of a test string, from the string action. In a certain case, the
equation is basically same as one derived by Papapetrou, Dixon and Wald for a
test extended body. We also discuss the force balance using a stringy probe
particle for an exact spinning multi-soliton solution of
Einstein-Maxwell-Dilaton-Axion theory. It is well known that the force balance
condition yields the saturation of the Bogomol'nyi type bound in the lowest
order. In the present formulation the gyromagnetic ratio of the stringy probe
particle is automatically determined to be which is the same value as the
background soliton. As a result we can confirm the force balance via the
gravitational spin-spin interaction.Comment: 8 pages, references added, comments added, Phys. Rev. D accepte
The Speciality Index as invariant indicator in the BKL Mixmaster Dynamics
The speciality index, which has been mainly used in Numerical Relativity for
studying gravitational waves phenomena as an indicator of the special or
non-special Petrov type character of a spacetime, is applied here in the
context of Mixmaster cosmology, using the Belinski-Khalatnikov-Lifshitz map.
Possible applications for the associated chaotic dynamics are discussed
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