276 research outputs found
Global monopole as dual-vacuum solution in Kaluza-Klein spacetime
By application of the duality transformation, which implies interchange of
active and passive electric parts of the Riemann curvature (equivalent to
interchange of Ricci and Einstein tensors) it is shown that the global monopole
solution in the Kaluza-Klein spacetime is dual to the corresponding vacuum
solution. Further we also obtain solution dual to flat space which would in
general describe a massive global monopole in 4-dimensional Euclidean space and
would have massless limit analogus to the 4-dimensional dual-flat solution.Comment: 8 pages, LaTEX versio
A spacetime dual to the NUT spacetime
By decomposing the Riemann curvature into electric and magnetic parts, a
duality transformation, which involves interchange of active and passive
electric parts, has recently been proposed. It was shown that the Schwarzschild
solution is dual to the one that describes the Schwarzschild particle with
cloud of string dust or a global monopole. Following the same procedure we
obtain the solution dual to the NUT spacetime.Comment: 10 pages, Latex. Accepted for publication in Classical and Quantum
Gravit
Electromagnetic duality in general relativity
By resolving the Riemann curvature relative to a unit timelike vector into
electric and magnetic parts, we consider duality relations analogous to the
electromagnetic theory. It turns out that the duality symmetry of the Einstein
action implies the Einstein vacuum equation without the cosmological term. The
vacuum equation is invariant under interchange of active and passive electric
parts giving rise to the same vacuum solutions but the gravitational constant
changes sign. Further by modifying the equation it is possible to construct
interesting dual solutions to vacuum as well as to flat spacetimes.Comment: 18 pages, LaTEX versio
A duality relation for fluid spacetime
We consider the electromagnetic resolution of gravitational field. We show
that under the duality transformation, in which active and passive electric
parts of the Riemann curvature are interchanged, a fluid spacetime in comoving
coordinates remains invariant in its character with density and pressure
transforming, while energy flux and anisotropic pressure remaining unaltered.
Further if fluid admits a barotropic equation of state,
where , which will transform to . Clearly the stiff fluid and dust are dual to each-other
while , will go to flat spacetime. However the n and the deSitter ) universes ar e self-dual.Comment: 5 pages, LaTeX version, Accepted in Classical Quantum Gravity as a
Lette
Inhomogeneous imperfect fluid spherical models without Big-Bang singularity
So far all known singularity-free cosmological models are cylindrically
symmetric. Here we present a new family of spherically symmetric non-singular
models filled with imperfect fluid and radial heat flow, and satisfying the
weak and strong energy conditions. For large anisotropy in pressure and
heat flux tend to vanish leading to a perfect fluid. There is a free function
of time in the model, which can be suitably chosen for non-singular behaviour
and there exist multiplicity of such choices.Comment: 8 pages, LaTeX versio
Spherical collapse with heat flow and without horizon
We present a class of solutions for a heat conducting fluid sphere, which
radiates energy during collapse without the appearance of horizon at the
boundary at any stage of the collapse. A simple model shows that there is no
accumulation of energy due to collapse since it radiates out at the same rate
as it is being generated.Comment: RevTeX, 3 page
Matter without matter: novel Kaluza-Klein spacetime in Einstein-Gauss-Bonnet gravity
We consider Einstein-Gauss-Bonnet gravity in -dimensional
Kaluza-Klein spacetime {\ma M}^{4} \times {\ma K}^{n-4}, where {\ma
K}^{n-4} is the Einstein space with negative curvature. In the case where
{\ma K}^{n-4} is the space of negative constant curvature, we have recently
obtained a new static black-hole solution (Phys. Rev. D {\bf 74}, 021501(R)
(2006), hep-th/0605031) which is a pure gravitational creation including
Maxwell field in four-dimensional vacuum spacetime. The solution has been
generalized to make it radially radiate null radiation representing
gravitational creation of charged null dust. The same class of solutions though
exists in spacetime {\ma M}^{d} \times {\ma K}^{n-d} for , however the
gravitational creation of the Maxwell field is achieved only for . Also,
Gauss-Bonnet effect could be brought down to {\ma M}^d only for .
Further some new exact solutions are obtained including its analogue in
Taub-NUT spacetime on {\ma M}^4 for .Comment: 13 pages, 1 figure, result for corrected, 3 references added,
final version to appear in Phys. Rev.
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