Browsing by Author "Nkosi, Zakhele Thomas"

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    Some investigation into causal viscous cosmological models with varieble Lambda
    (2001) Nkosi, Zakhele Thomas; Beesham, A.
    In this thesis we investigate the evolution of viscous Friedmann-Lemaitre-Robertson-Walker models with a variable cosmological term. The numerical solutions are obtained and represented graphically. Each graph depends on the value of gamma. The present values of the deceleration parameter and density parameter were obtained by using Eckart theory and the truncated theory and given in the tabular form. Power law solutions for the Hubble parameter are shown to exist and we give the values of all the other cosmological variables. The behaviour of the temperature depends on the initial conditions. Furthermore, the equations are also transformed into a plane autonomous system by using dimensionless variables and a dimensionless equation of state, and the qualitative behaviour of the system is investigated. The sets of equilibrium points are determined and their behaviour discussed. The exact value of the Hubble parameter, cosmological term, bulk viscosity pressure and the energy density are obtained and discussed.