338 research outputs found
Accelerated Levi-Civita-Bertotti-Robinson Metric in D-Dimensions
A conformally flat accelerated charge metric is found in an arbitrary
dimension . It is a solution of the Einstein-Maxwell-null fluid with a
cosmological constant in dimensions. When the acceleration is zero
our solution reduces to the Levi-Civita-Bertotti-Robinson metric. We show that
the charge loses its energy, for all dimensions, due to the acceleration.Comment: Latex File, 12 page
Closed timelike curves and geodesics of Godel-type metrics
It is shown explicitly that when the characteristic vector field that defines
a Godel-type metric is also a Killing vector, there always exist closed
timelike or null curves in spacetimes described by such a metric. For these
geometries, the geodesic curves are also shown to be characterized by a lower
dimensional Lorentz force equation for a charged point particle in the relevant
Riemannian background. Moreover, two explicit examples are given for which
timelike and null geodesics can never be closed.Comment: REVTeX 4, 12 pages, no figures; the Introduction has been rewritten,
some minor mistakes corrected, many references adde
G\"odel Type Metrics in Three Dimensions
We show that the G{\" o}del type Metrics in three dimensions with arbitrary
two dimensional background space satisfy the Einstein-perfect fluid field
equations. There exists only one first order partial differential equation
satisfied by the components of fluid's velocity vector field. We then show that
the same metrics solve the field equations of the topologically massive gravity
where the two dimensional background geometry is a space of constant negative
Gaussian curvature. We discuss the possibility that the G{\" o}del Type Metrics
to solve the Ricci and Cotton flow equations. When the vector field
is a Killing vector field we finally show that the stationary G{\" o}del Type
Metrics solve the field equations of the most possible gravitational field
equations where the interaction lagrangian is an arbitrary function of the
electromagnetic field and the curvature tensors.Comment: 17 page
Godel-type Metrics in Various Dimensions II: Inclusion of a Dilaton Field
This is the continuation of an earlier work where Godel-type metrics were
defined and used for producing new solutions in various dimensions. Here a
simplifying technical assumption is relaxed which, among other things,
basically amounts to introducing a dilaton field to the models considered. It
is explicitly shown that the conformally transformed Godel-type metrics can be
used in solving a rather general class of Einstein-Maxwell-dilaton-3-form field
theories in D >= 6 dimensions. All field equations can be reduced to a simple
"Maxwell equation" in the relevant (D-1)-dimensional Riemannian background due
to a neat construction that relates the matter fields. These tools are then
used in obtaining exact solutions to the bosonic parts of various supergravity
theories. It is shown that there is a wide range of suitable backgrounds that
can be used in producing solutions. For the specific case of (D-1)-dimensional
trivially flat Riemannian backgrounds, the D-dimensional generalizations of the
well known Majumdar-Papapetrou metrics of general relativity arise naturally.Comment: REVTeX4, 17 pp., no figures, a few clarifying remarks added and
grammatical errors correcte
Gurses' Type (b) Transformations are Neighborhood-Isometries
Following an idea close to one given by C. G. Torre (private communication),
we prove that Riemannian spaces (M,g) and (M,h) that are related by a Gurses
type (b) transformation [M. Gurses, Phys. Rev. Lett. 70, 367 (1993)] or,
equivalently, by a Torre-Anderson generalized diffeomorphism [C. G. Torre and
I. M. Anderson, Phys. Rev. Lett. xx, xxx (1993)] are neighborhood-isometric,
i.e., every point x in M has a corresponding diffeomorphism phi of a
neighborhood V of x onto a generally different neighborhood W of x such that
phi*(h|W) = g|V.Comment: 10 pages, LATEX, FJE-93-00
Photon rockets moving arbitrarily in any dimension
A family of explicit exact solutions of Einstein's equations in four and
higher dimensions is studied which describes photon rockets accelerating due to
an anisotropic emission of photons. It is possible to prescribe an arbitrary
motion, so that the acceleration of the rocket need not be uniform - both its
magnitude and direction may vary with time. Except at location of the
point-like rocket the spacetimes have no curvature singularities, and
topological defects like cosmic strings are also absent. Any value of a
cosmological constant is allowed. We investigate some particular examples of
motion, namely a straight flight and a circular trajectory, and we derive the
corresponding radiation patterns and the mass loss of the rockets. We also
demonstrate the absence of "gravitational aberration" in such spacetimes. This
interesting member of the higher-dimensional Robinson-Trautman class of pure
radiation spacetimes of algebraic type D generalises the class of Kinnersley's
solutions that has long been known in four-dimensional general relativity.Comment: Text and figures modified (22 pages, 8 figures). To appear in the
International Journal of Modern Physics D, Vol. 20, No..
Lienard-Wiechert Potentials in Even Dimensions
The motion of point charged particles is considered in an even dimensional Minkowski space-time. The potential functions corresponding to the massless scalar and the Maxwell fields are derived algorithmically. It is shown that in all even dimensions particles lose energy due to acceleration
Colliding gravitational plane waves in dilaton gravity
Collision of plane waves in dilaton gravity theories and low energy limit of string theory is considered. The formulation of the the problem and some exact solutions are presented
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