In this Thesis, using the orthonormal tetrad formalism, we give a systematic and detailed derivation of the full set of cosmic evolution and constraint equations in Bianchi-type and Robertson-Walker (RW) models containing an orthogonal, one-component fluid. It is then shown explicitly how the cosmological evolution equations can be written as an autonomous system of first order ordinary differential equations in terms of dimensionless variables. The application of the dynamical systems analysis is illustrated in flat and also in open RW models with a cosmological term Λ, using a perfect fluid source with a linear barotropic equation of state : p = ( – 1) . As an alternative to this conventional fluid, we consider an exotic fluid known as (generalised) Chaplygin gas with an equation of state : p = – A/α , and we give, for the first time, a dynamical systems analysis for it. We find that in flat and open RW models, assuming a zero cosmological constant, the past attractor is a pressureless flat Friedmann model and the future attractor is the one which mimics the behaviour of a de Sitter model which is inflationary. From this, we conclude that the Chaplygin gas can be considered as playing the role of a positive cosmological constant. The result doesn’t depend on the values of the parameter α.
DULDA Ayşe ,
Danışman : Prof.Dr.Çetin ARIKAN
Anabilim dalı : Fizik
Program : Katıhal Fiziği
Yılı : 2006
Tez savunma Jürisi : Prof.Dr.Çetin ARIKAN (Danışman)
Prof.Dr.Tevfik Osman ÖZKAN
Prof.Dr.İbrahim YUSUFOĞLU
Yrd.Doç.Dr.Ayşe EROL
Prof.Dr.Sevim AKYÜZ
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