IUCAA Preprints
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Item On the brown-york quasilocal energy, gravitational charge, and black hole event horizons(2015-03-13) Bose, Sukanta; Dadhich, NareshWe prove the recently proposed identity for certain black hole spacetimes that relates the difference of the Brown-York quasilocal energy and the Komar charge at the event horizon of the hole to the total energy of the spacetime. We prove this identity for the Kerr-Newman family of black hole spacetimes and for non-static (cosmological) spherically symmetric shear-free perfect fluid solutions of general relativity that contain black hole event horizons. We explicitly demonstrate its validity by applying it to several asymptotically fiat as well as non-fiat black hole solutions, including the case of a black hole with a global monopole charge.Item New classes of black hole spacetime in 2+1 gravity(2015-03-01) Bose, Sukanta; Dadhich, Naresh; Kar, SyanNew 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.Item Gravoelectric-dual of the kerr solution(2015-03-01) Dadhich, Naresh; Patel, L.K.By decomposing the Riemann curvature into electric and magnetic parts, we define the gravoelectric duality transformation by interchange of active and passive electric parts which amounts to interchange of the Ricci and Einstein tensors. It turns out that the vacuum equation is duality-invariant. We obtain solutions dual to the Kerr solution by writing an effective vacuum equation in such a way that it still admits the Kerr solution but is not duality invariant. The dual equation is then solved to obtain the dual-Kerr solution which can be interpreted as the Kerr black hole sitting in a string dust universe.Item On gravitational charge of stationary spacetimes(2014-11-23) Dadhich, NareshWe point out that ours is a definition of gravitational charge and not of quasilocal mass [1] we have defined gravitational charge as the flux of effective gravitational acceleration across a closed 2- surface. It turns out that tidal force can change its sense from convergence to divergence outside the horizon for suitable range of values of rotation and electric charge parameters of the black hole.Item On active and passive gravitational mass of fluid sphere(2014-11-23) Dadhich, Naresh