2000 (IPP)

Permanent URI for this collectionhttp://localhost:4000/handle/11007/629

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Author: search.filters.author.Dadhich, Naresh

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Now showing 1 - 7 of 7
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    On product spacetime with 2-sphere of constant curvature
    (2000-10-10) Dadhich, Naresh
    If we consider the spacetime manifold as product of a constant curvature 2-sphere (hypersphere) and a 2-space, then solution of the Einstein equation requires that the latter must also be of constant curvature. There exist only two solutions for classical matter dis- tribution which are given by the Nariai (anti) metric describing an Einstein space and the Bertotti - Robinson (anti) metric describing a uniform electric field. These two solutions are transformable into each other by letting the timelike convergence density change sign. The hy- perspherical solution is anti of the spherical one and the vice -versa. For non classical matter, we however find a new solution, which is electrograv dual to the flat space, and describes a cloud of string dust of uniform energy density. We also discuss some interesting features of the particle motion in the Bertotti - Robinson metric.
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    On naked singularities in higher dimensional Vaidya space-times
    (2000-08-16) Ghosh, S. G.; Dadhich, Naresh
    We investigate the end state of gravitational collapse of null fluid in higher di- mensional space-times. Both naked singularities and black holes are shown to be developing as final outcome of the collapse. The naked singularity spectrum in col- lapsing Vaidya region (4D) gets covered with increase in dimensions and hence higher dimensions favor black hole in comparison to naked singularity. The Cosmic Censor- ship Conjecture will be fully respected for a space of infinite dimension.
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    On a peculiar family of static, axisymmetric, vacuum solutions of the Einstein equations
    (2000-07-14) Dadhich, Naresh; Date, G.
    The Zipoy-Voorhees family of static, axisymmetric vacuum solutions orms an interesting family in that it contains the Schwarzschild black hole excepting which all other members have naked singularity. We ana- yze some properties of the region near singularity by studying a natural amily of 2-surfaces. We establish that these have the topology of the 2-sphere by an application of the Gauss-Bonnet theorem. By computing he area, we establish that the singular region is ‘point-like’. Isometric mbedding of these surfaces in the three dimensional Euclidean space is used to distinguish the two types of deviations from spherical symmetry.
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    Negative Energy Condition and Black Holes on the Brane
    (2000-02-24) Dadhich, Naresh
    We propose that for non-localizable energy distribution the rele- vant energy condition is determined by the gravitational field energy which is negative for positive non-gravitational energy. That is neg- ativity of the non-localized energy is the ”positive” energy condition. This would have direct application and relevance for a black hole on the brane which would be sitting in a trace free stresses induced by the Weyl curvature of the bulk.
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    Inheriting geodesic flows
    (2000-12-12) Lortan, D. B.; Maharaj, S. D.; Dadhich, Naresh
    We investigate the propagation equations for the expansion, vorticity and shear for per- fect fluid space-times which are geodesic. It is assumed that space-time admits a conformal Killing vector which is inheriting so that fluid flow lines are mapped conformally. Simple constraints on the electric and magnetic parts of the Weyl tensor are found for conformal symmetry. For homothetic vectors the vorticity and shear are free; they vanish for nonhomothetic vectors. We prove a conjecture for conformal symmetries in the special case of inheriting geodesic flows: there exist no proper con- formal Killing vectors ( ;ab =0) for perfect fluids except for Robertson–Walker space-times. For a nonhomothetic vector field the propagation of the quantityln(Rabuaub ) along the integral curves of the symmetry vector is homogeneous.
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    Global monopoles and scalar fields as the electrogravity dual of Schwarzschild spacetime
    (2000-08-15) Dadhich, Naresh; Banerjee, Narayan
    We prove that both global monopole and minimally coupled static zero mass scalar field are electrogravity dual of the Schwarzschild solution or flat space and they share the same equation of state, T0 0 − Ti i = 0. This property was however known for the global monopole spacetime while it is for the first time being established for the scalar field. In particular, it turns out that the Xanthopoulos - Zannias scalar field solution is dual to flat space.