719 research outputs found
Loop Variables for a Class of Conical Spacetimes
Loop variables are used to describe the presence of topological defects in
spacetime. In particular we study the dependence of the holonomy transformation
on angular momentum and torsion for a multi-chiral cone. We also compute the
holonomies for multiple moving crossed cosmic strings and two plane topological
defects-crossed by a cosmic string.Comment: 17 pages, LATE
Spacetime Defects: von K\'arm\'an vortex street like configurations
A special arrangement of spinning strings with dislocations similar to a von
K\'arm\'an vortex street is studied. We numerically solve the geodesic
equations for the special case of a test particle moving along twoinfinite rows
of pure dislocations and also discuss the case of pure spinning defects.Comment: 9 pages, 2figures, CQG in pres
Local And Global Structure Of A Thick-domain-wall Space-time
The local and global properties of the Goetz thick plane domain-wall space-time are studied. It is found that when the surface energy of the wall is greater than a critical value c, the space-time will be closed by intermediate singularities at a finite proper distance. A model is presented in which these singularities will give rise to scalar ones when interacting with null fluids. The maximum extension of the space-time of the wall whose surface energy is less than c is presented. It is shown that for a certain choice of the free parameter the space-time has a black hole structure but plane symmetry. © 1995 The American Physical Society.5112R6612R661
Geodesics around Weyl-Bach's Ring Solution
We explore some of the gravitational features of a uniform ring both in the
Newtonian potential theory and in General Relativity. We use a spacetime
associated to a Weyl static solution of the vacuum Einstein's equations with
ring like singularity. The Newtonian motion for a test particle in the
gravitational field of the ring is studied and compared with the corresponding
geodesic motion in the given spacetime. We have found a relativistic peculiar
attraction: free falling particle geodesics are lead to the inner rim but never
hit the ring.Comment: 8 figures, 14 pages. LaTeX w/ subfigure, graphic
Exact General Relativistic Disks with Magnetic Fields
The well-known ``displace, cut, and reflect'' method used to generate cold
disks from given solutions of Einstein equations is extended to solutions of
Einstein-Maxwell equations. Four exact solutions of the these last equations
are used to construct models of hot disks with surface density, azimuthal
pressure, and azimuthal current. The solutions are closely related to Kerr,
Taub-NUT, Lynden-Bell-Pinault and to a one-soliton solution. We find that the
presence of the magnetic field can change in a nontrivial way the different
properties of the disks. In particular, the pure general relativistic
instability studied by Bicak, Lynden-Bell and Katz [Phys. Rev. D47, 4334, 1993]
can be enhanced or cured by different distributions of currents inside the
disk. These currents, outside the disk, generate a variety of axial symmetric
magnetic fields. As far as we know these are the first models of hot disks
studied in the context of general relativity.Comment: 21 pages, 11 figures, uses package graphics, accepted in PR
Un alcance sobre la hipótesis de no-deslizamiento en flujo viscoso
Se analiza establecimiento en el tiempo de flujo de Poiseuille con deslizamiento del fluido en la pared. Se pone en evidencia que en estas circunstancias el flujo presentaría características inaceptables desde el punto de vista físico y matemático. De este modo, se concluye que el presente estudio constituye un principio de demostración analítica parcial de la necesidad de la hipótesis de no-deslizamiento en la pared del dueto
Acceleration, streamlines and potential flows in general relativity: analytical and numerical results
Analytical and numerical solutions for the integral curves of the velocity
field (streamlines) of a steady-state flow of an ideal fluid with
equation of state are presented. The streamlines associated with an accelerate
black hole and a rigid sphere are studied in some detail, as well as, the
velocity fields of a black hole and a rigid sphere in an external dipolar field
(constant acceleration field). In the latter case the dipole field is produced
by an axially symmetric halo or shell of matter. For each case the fluid
density is studied using contour lines. We found that the presence of
acceleration is detected by these contour lines. As far as we know this is the
first time that the integral curves of the velocity field for accelerate
objects and related spacetimes are studied in general relativity.Comment: RevTex, 14 pages, 7 eps figs, CQG to appea
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