138 research outputs found
Nonexpanding impulsive gravitational waves with an arbitrary cosmological constant
Exact solutions for nonexpanding impulsive waves in a background with nonzero
cosmological constant are constructed using a `cut and paste' method. These
solutions are presented using a unified approach which covers the cases of de
Sitter, anti-de Sitter and Minkowski backgrounds. The metrics are presented in
continuous and distributional forms, both of which are conformal to the
corresponding metrics for impulsive pp-waves, and for which the limit as
can be made explicitly.Comment: 5 pages, LaTeX. To appear in Phys. Lett.
Chaos in a modified Henon-Heiles system describing geodesics in gravitational waves
A Hamiltonian system with a modified Henon-Heiles potential is investigated.
This describes the motion of free test particles in vacuum gravitational
pp-wave spacetimes with both quadratic ("homogeneous") and cubic
("non-homogeneous") terms in the structural function. It is shown that, for
energies above a certain value, the motion is chaotic in the sense that the
boundaries separating the basins of possible escapes become fractal.
Similarities and differences with the standard Henon-Heiles and the monkey
saddle systems are discussed. The box-counting dimension of the basin
boundaries is also calculated.Comment: 11 pages, 7 figures, LaTeX. To appear in Phys. Lett.
Geodesics in spacetimes with expanding impulsive gravitational waves
We study geodesic motion in expanding spherical impulsive gravitational waves
propagating in a Minkowski background. Employing the continuous form of the
metric we find and examine a large family of geometrically preferred geodesics.
For the special class of axially symmetric spacetimes with the spherical
impulse generated by a snapping cosmic string we give a detailed physical
interpretation of the motion of test particles.Comment: 12 pages, Revtex, final versio
Symmetries and geodesics in (anti-)de Sitter spacetimes with nonexpanding impulsive waves
We consider a class of exact solutions which represent nonexpanding impulsive
waves in backgrounds with nonzero cosmological constant. Using a convenient
5-dimensional formalism it is shown that these spacetimes admit at least three
global Killing vector fields. The same geometrical approach enables us to find
all geodesics in a simple explicit form and describe the effect of impulsive
waves on test particles. Timelike geodesics in the axially-symmetric
Hotta-Tanaka spacetime are studied in detail. It is also demonstrated that for
vanishing cosmological constant, the symmetries and geodesics reduce to those
for well-known impulsive pp-waves.Comment: 16 pages, 3 figures, LaTeX 2e. To appear in Class. Quantum Gra
Accelerating Kerr-Newman black holes in (anti-)de Sitter space-time
A class of exact solutions of the Einstein-Maxwell equations is presented
which describes an accelerating and rotating charged black hole in an
asymptotically de Sitter or anti-de Sitter universe. The metric is presented in
a new and convenient form in which the meaning of the parameters is clearly
identified, and from which the physical properties of the solution can readily
be interpreted.Comment: 5 pages. To appear in Phys. Rev.
Impulsive waves in electrovac direct product spacetimes with Lambda
A complete family of non-expanding impulsive waves in spacetimes which are
the direct product of two 2-spaces of constant curvature is presented. In
addition to previously investigated impulses in Minkowski, (anti-)Nariai and
Bertotti-Robinson universes, a new explicit class of impulsive waves which
propagate in the exceptional electrovac Plebanski-Hacyan spacetimes with a
cosmological constant Lambda is constructed. In particular, pure gravitational
waves generated by null particles with an arbitrary multipole structure are
described. The metrics are impulsive members of a more general family of the
Kundt spacetimes of type II. The well-known pp-waves are recovered for
Lambda=0.Comment: 6 pages, 1 figure, LaTeX 2e. To appear in Class. Quantum Gra
Generalised Kundt waves and their physical interpretation
We present the complete family of space-times with a non-expanding,
shear-free, twist-free, geodesic principal null congruence (Kundt waves) that
are of algebraic type III and for which the cosmological constant ()
is non-zero. The possible presence of an aligned pure radiation field is also
assumed. These space-times generalise the known vacuum solutions of type N with
arbitrary and type III with . It is shown that there
are two, one and three distinct classes of solutions when is
respectively zero, positive and negative. The wave surfaces are plane,
spherical or hyperboloidal in Minkowski, de Sitter or anti-de Sitter
backgrounds respectively, and the structure of the family of wave surfaces in
the background space-time is described. The weak singularities which occur in
these space-times are interpreted in terms of envelopes of the wave surfaces.Comment: 16 pages including 2 figures. To appear in Classical and Quantum Gra
Non-expanding impulsive gravitational waves
We investigate a class of impulsive gravitational waves which propagate
either in Minkowski or in the (anti-)de Sitter background. These waves are
constructed as impulsive members of the Kundt class of
non-twisting, non-expanding type N solutions of vacuum Einstein equations with
a cosmological constant . We show that the only non-trivial waves of
this type in Minkowski spacetime are impulsive pp-waves. For we
demonstrate that the canonical subclasses of , which are
invariantly different for smooth profiles, are all locally equivalent for
impulsive profiles. Also, we present coordinate system for these impulsive
solutions which is explicitly continuous.Comment: 12 pages, to appear in Class. Quantum Gra
An interpretation of Robinson-Trautman type N solutions
The Robinson-Trautman type N solutions, which describe expanding
gravitational waves, are investigated for all possible values of the
cosmological constant Lambda and the curvature parameter epsilon. The wave
surfaces are always (hemi-)spherical, with successive surfaces displaced in a
way which depends on epsilon. Explicit sandwich waves of this class are studied
in Minkowski, de Sitter or anti-de Sitter backgrounds. A particular family of
such solutions which can be used to represent snapping or decaying cosmic
strings is considered in detail, and its singularity and global structure is
presented.Comment: 13 pages, 3 figures. To appear in Class. Quantum Gra
Continuous coordinates for all impulsive pp - waves
We present a coordinate system for a general impulsive gravitational pp -
wave in vacuum in which the metric is explicitly continuous, synchronous and
"transverse". Also, it is more appropriate for investigation of particle
motions.Comment: 4 pages, LaTeX, no figures, to be published in Phys. Lett.
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