Yazar "Kamdi, Vaishali" seçeneğine göre listele

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    Early viscous universe with variable cosmological and gravitational constants in higher dimensional space time
    (Springer Science+Business Media, LLC, part of Springer Nature, 2008) Khadekar, G. S.; Kondawar, Gopal L.; Kamdi, Vaishali; Özel, Cenap
    In this paper we present a number of classes of solutions of the Einstein's field equations with variable G, Lambda and bulk viscosity for a Kaluza-Klein type of cosmological model. The solutions are obtained by using gamma-law equation of state p = (gamma - 1)rho, where adiabatic parameter gamma-varies continuously as the universe expand. A unified description of the early evolution of the universe is discussed with number of possible assumption on the bulk viscous term and gravitational constant in which an inflationary phase followed by radiation-dominated phase. We also investigate the cosmological model with constant and time dependent bulk viscosity along with constant and time dependent gravitational constant. In all cases, the cosmological constant Lambda found to be positive and decreasing function of time which supports the results obtained from recent supernovae Ia observations. The important physical behaviour of the early cosmological model has also been discussed in the frame work of higher dimensional space-time.
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    Higher dimensional lambda-CDM üniverse: A phenomenological approach with many possibilities
    (Springer/Plenum Publishers, 2009) Khadekar, G. S.; Kamdi, Vaishali; Özel, Cenap
    In this paper we investigate the Lambda-CDM universe by selecting the specific time dependent form of Lambda, viz. (Lambda) over dot proportional to H(3), in the context of 5- dimensional space time. Time-dependent form of equation of state parameter w is derived along with a possible signature flip of deceleration parameter q. It is also observed that a present age of the Universe, calculated for some specific values of parameter agrees very well with the observational data.
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    Higher dimensional unified description of early universe with variable gravitational and cosmological constants
    (Springer/Plenum Publishers, 2008) Khadekar, G. S.; Kondawar, Gopal L.; Kamdi, Vaishali; Özel, Cenap
    In this paper we consider the five dimensional cosmological model with variable gravitational and cosmological constants in the presence of perfect fluid in Kaluza-Klein theory of gravitation. The exact solutions of the field equations are obtained by using the gamma law equation of state p=(gamma-1)rho in which the parameter gamma depends on scale factor R. A unified description of early universe is presented with the assumption Lambda = beta H(2) supercript stop in which inflationary phase is followed by radiation dominated phase. The various physical aspects of the cosmological models are also discussed in the framework of higher dimensional space time.