3,690 research outputs found
Lattice Universes in 2+1-dimensional gravity
Lattice universes are spatially closed space-times of spherical topology in
the large, containing masses or black holes arranged in the symmetry of a
regular polygon or polytope. Exact solutions for such spacetimes are found in
2+1 dimensions for Einstein gravity with a non-positive cosmological constant.
By means of a mapping that preserves the essential nature of geodesics we
establish analogies between the flat and the negative curvature cases. This map
also allows treatment of point particles and black holes on a similar footing.Comment: 14 pages 7 figures, to appear in Festschrift for Vince Moncrief (CQG
Collapse of Kaluza-Klein Bubbles
Kaluza-Klein theory admits ``bubble" configurations, in which the
circumference of the fifth dimension shrinks to zero on some compact surface. A
three parameter family of such bubble initial data at a moment of time-symmetry
(some including a magnetic field) has been found by Brill and Horowitz,
generalizing the (zero-energy) ``Witten bubble" solution. Some of these data
have negative total energy. We show here that all the negative energy bubble
solutions start out expanding away from the moment of time symmetry, while the
positive energy bubbles can start out either expanding or contracting. Thus it
is unlikely that the negative energy bubbles would collapse and produce a naked
singularity.Comment: 6 pages, plain LaTeX, UMDGR-94-08
Integrability of the N-body problem in (2+1)-AdS gravity
We derive a first order formalism for solving the scattering of point sources
in (2+1) gravity with negative cosmological constant. We show that their
physical motion can be mapped, with a polydromic coordinate transformation, to
a trivial motion, in such a way that the point sources move as time-like
geodesics (in the case of particles) or as space-like geodesics (in the case of
BTZ black holes) of a three-dimensional hypersurface immersed in a
four-dimensional Minkowskian space-time, and that the two-body dynamics is
solved by two invariant masses, whose difference is simply related to the total
angular momentum of the system.Comment: 15 pages, LaTeX, no figure
In Love\u27s Bouquet
https://digitalcommons.library.umaine.edu/mmb-vp/3617/thumbnail.jp
Perturbative Analysis of the Two-body Problem in (2+1)-AdS gravity
We derive a perturbative scheme to treat the interaction between point
sources and AdS-gravity. The interaction problem is equivalent to the search of
a polydromic mapping , endowed with 0(2,2) monodromies,
between the physical coordinate system and a Minkowskian 4-dimensional
coordinate system, which is however constrained to live on a hypersurface. The
physical motion of point sources is therefore mapped to a geodesic motion on
this hypersuface. We impose an instantaneous gauge which induces a set of
equations defining such a polydromic mapping. Their consistency leads naturally
to the Einstein equations in the same gauge. We explore the restriction of the
monodromy group to O(2,1), and we obtain the solution of the fields
perturbatively in the cosmological constant.Comment: 19 pages, no figures, LaTeX fil
Black Hole Thermodynamics and Riemann Surfaces
We use the analytic continuation procedure proposed in our earlier works to
study the thermodynamics of black holes in 2+1 dimensions. A general black hole
in 2+1 dimensions has g handles hidden behind h horizons. The result of the
analytic continuation is a hyperbolic 3-manifold having the topology of a
handlebody. The boundary of this handlebody is a compact Riemann surface of
genus G=2g+h-1. Conformal moduli of this surface encode in a simple way the
physical characteristics of the black hole. The moduli space of black holes of
a given type (g,h) is then the Schottky space at genus G. The (logarithm of
the) thermodynamic partition function of the hole is the Kaehler potential for
the Weil-Peterson metric on the Schottky space. Bekenstein bound on the black
hole entropy leads us to conjecture a new strong bound on this Kaehler
potential.Comment: 17+1 pages, 9 figure
GEMPAK5 user's guide, version 5.0
GEMPAK is a general meteorological software package used to analyze and display conventional meteorological data as well as satellite derived parameters. The User's Guide describes the GEMPAK5 programs and input parameters and details the algorithms used for the meteorological computations
Black Holes and Causal Structure in Anti-de Sitter Isometric Spacetimes
The observation that the 2+1 dimensional BTZ black hole can be obtained as a
quotient space of anti-de Sitter space leads one to ask what causal behaviour
other such quotient spaces can display. In this paper we answer this question
in 2+1 and 3+1 dimensions when the identification group has one generator.
Among other things we find that there does not exist any 3+1 generalization of
the rotating BTZ hole. However, the non-rotating generalization exists and
exhibits some unexpected properties. For example, it turns out to be non-static
and to possess a non-trivial apparent horizon.Comment: LaTeX, 22 pages, 10 postscript figures, uses epsf.te
Positive Definiteness of Gravitational Field Energy
The total gravitational field energy functional is shown to have only one extremum under variation of the metric field variables. At the extremum the energy vanishes and space is flat; second variation shows that the vacuum state is also a local minimum
The isolation of gravitational instantons: Flat tori V flat R^4
The role of topology in the perturbative solution of the Euclidean Einstein
equations about flat instantons is examined.Comment: 15 pages, ICN-UNAM 94-1
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