IUCAA Preprints
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Item Cylindrically symmetric cosmological models in the Kaluza-Klein space time(2015-01-27) Patel, L.K.; Dadhich, NareshWe consider a non-diagonal cylindrically symmetric metric in the Kaluza-Klein spacetime. We obtain a number of homogeneous and inhomogeneous perfect fluid cosmological models, which include the 5-dimensional analogue of the recently found 4-dimensional non-singular stiff fluid model. Amongst the homogeneous models, which are all as expected big-bang singular, there is the 5-dimensional version of the Friedman-Robertson-Walker flat model.Item On singularity free cosmological model(2015-01-13) Dadhich, Naresh; Tikekar, R.; Patel, L.K.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 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.