IUCAA Preprints

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    sdfsdjinfdbfudhgu
    (2014-01-12)
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    New classes of black hole spacetime in 2+1 gravity
    (2015-03-01) Bose, Sukanta; Dadhich, Naresh; Kar, Syan
    New multi-parameter families of black holes in three-dimensional (3D) gravity are obtained. We apply the electrogravity transformation (which implies an exchange of the Ricci and Einstein tensors) to the 3D field equations to obtain these solutions. Several properties of these geometries, including the nature of the matter that threads them, are discussed. Some of these properties are found to be strikingly different from known black holes in (2+1) dimensions.
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    Behaviour of lagrangian approximations in spherical voids
    (2015-02-07) Sahni, Varun; Shandarin, S.F.
    We study the behaviour of spherical voids in Lagrangian perturbation theories L(n), of which the Zel'dovich approximation is the lowest order solution L(1). We find that at early times higher order L(n), give an increasingly accurate picture of void expansion. However, at late times particle trajectories in L (2) begin to turnaround and converge leading to the contraction of a void, a sign of pathological behaviour. By contrast particle trajectories in L(3) are well behaved and this approximation gives results in excellent agreement with the exact top-hat solution as long as the void is not too underdense. For very underdense voids, L (3) evacuates the void much too rapidly, leading us to conclude that the Zel'dovich approximation L(1) remains the best approximation to apply to the late-time study of voids. The behaviour of high-order Lagrangian approximations in spherical voids is typical for asymptotic (semiconvergent) series and may be generic for Lagrangian perturbation theory.