1992 (IPP)
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Item Cylindrically symmetric viscous universes(2014-11-26) Patel, L.K.; Dadhich, NareshWe have considered here cylindrically symmetric cosmological models with viscous fluid having the Kasnerian time evolution. It turns out that the ‘‘no‐matter’’ limit of our geodetic viscous universes, which can as well be looked upon as string dust universes, is the non-flat empty Kasner spacetime. We thus propose that the universe may be born with the Kasner geometry at t = 0 with matter in the form of viscous fluid, then it may follow the path: geodetic to non-geodetic and finally to the radiation phase when viscosity is fully worn out. We have solutions to describe each phase separately.Item Cylindrical universes with heat and null radiation flow(2014-11-25) Patel, L.K.; Dadhich, NareshIn paper-I(Patel and Dadhich ,1992) we have discussed cylindrically symmetric viscous fluid models with the Kasnerian time evolution. In this paper we incorporate heat flow and null radiation flow with the perfect fluid. Here again, in the case of heat flow the Kasner spacetime is the matter-free limit of the model. We establish a general result that a static perfect fluid distribution will on Kasnerization (introduce t4/3, t4/3, and t−2/3 in the coefficients of dr2, dΦ2, and dz2) yield a time-dependent distribution with the same equation of state and with or without heat flow.Item Singularity free inhomogeneous viscous fluid cosmological models(2014-11-23) Patel, L.K.; Dadhich, NareshWe obtain two new classes of singularity free inhomogeneous viscous fluid cosmological solutions, which reduce to the Senovilla [1] class when viscosity is switched off. It is interesting to note that inclusion of viscosity does not disturb the singularity free character and general behavior of the models remains qualitatively same.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