Now showing items 45-64 of 69

    • New classes of exact solutions for charged perfect fluids. 

      Mthethwa, Thulani Richard. (2014-03-28)
      We investigate techniques to generate new classes of exact solutions to the Einstein- Maxwell field equations which represent the gravitational field of charged perfect fluid spherically symmetric distributions of ...
    • New models for quark stars with charge and anisotropy. 

      Sunzu, Jefta Mvukaye. (2014)
      We find new classes of exact solutions for the Einstein-Maxwell field equations. The solutions are obtained by considering charged anisotropic matter with a linear equation of state consistent with quark stars. The field ...
    • New realistic solutions for charged matter with an equation of state. 

      Takisa, Pedro Mafa.
      The purpose of this thesis is to provide new exact solutions to the Einstein-Maxwell system which are physically reasonable. We assume that the spacetime is static and spherically symmetric with a charged anisotropic ...
    • Non-circularity of beams in the CMB polarization power spectrum estimation. 

      Ramamonjisoa, Fidy Andriamanankasina. (2015-01-05)
      Precise measurements of the Cosmic Microwave Background (CMB) anisotropies have been one of the foremost concerns in modern cosmology as it provides valuable information on the cosmology of the Universe. However, an ...
    • Nonclassical solutions of hyperbolic conservation laws. 

      Agbavon, Koffi Messan.
      This dissertation studies the nonclassical shock waves which appears as limits of certain type diffusive-dispersive regularisation to hyperbolic of conservation laws. Such shocks occur very often when the ux function ...
    • On new and improved semi-numerical techniques for solving nonlinear fluid flow problems. 

      Makukula, Zodwa Gcinaphi. (2012)
      Most real world phenomena is modeled by ordinary and/or partial differential equations. Most of these equations are highly nonlinear and exact solutions are not always possible. Exact solutions always give a good account ...
    • On singularly perturbed problems and exchange of stabilities. 

      Kimba Phongi, Eddy. (2015)
      Singular perturbation theory has been used for about a century to describe models displaying different timescales, that arise in applied sciences; particularly, models displaying two timescales, namely slow time and fast ...
    • On Stephani universes. 

      Moopanar, Selvandren. (1992)
      In this dissertation we study conformal symmetries in the Stephani universe which is a generalisation of the Robertson-Walker models. The kinematics and dynamics of the Stephani universe are discussed. The conformal ...
    • On the integrity of domination in graphs. 

      Smithdorf, Vivienne. (1993)
      This thesis deals with an investigation of the integrity of domination in a.graph, i.e., the extent to which domination properties of a graph are preserved if the graph is altered by the deletion of vertices or edges or ...
    • On the physical viability of horizon-free collapse. 

      Ntshangase, Mlungisi Alex Doctor. (2015-09-04)
      The so-called Cosmic Censorship Conjecture has drawn widespread attention amongst astrophysicists and particle physicists. In particular, the end-state of gravitational collapse of a bounded matter distribution is a ...
    • Optimisation of the population Monte Carlo algorithm : application to cosmology. 

      Moodley, Darell. (2015-09-04)
      In this thesis we study the Population Monte Carlo (PMC) algorithm and utilise simulations to improve the efficiency of the algorithm by optimising the algorithm parameters. We then ap ply these optimisation results to ...
    • Partial exchangeability and related topics. 

      North, Delia Elizabeth. (1991)
      Partial exchangeability is the fundamental building block in the subjective approach to the probability of multi-type sequences which replaces the independence concept of the objective theory. The aim of this thesis is ...
    • Relativistic spherical stars. 

      Mkhwanazi, Wiseman Thokozani. (1993)
      In this thesis we study spherically symmetric spacetimes which are static with a perfect fluid source. The Einstein field equations, in a number of equivalent forms, are derived in detail. The physical properties of a ...
    • Shear-free models for relativistic fluids with heat flow and pressure isotropy. 

      Brassel, Byron P. (2014)
      We model the interior dynamics of a relativistic radiating fuid in a nonstatic spher- ically symmetric spacetime. The matter distribution takes the form of an imperfect fuid with a nonvanishing radially directed heat ...
    • Solution generating algorithms in general relativity. 

      Krupanandan, Daniel D. (2011)
      We conduct a comprehensive investigative review of solution generating algorithms for the Einstein field equations governing the gravitational behaviour of an isolated neutral static spherical distribution of perfect ...
    • Some Mal'cev conditions for varieties of algebras. 

      Moses, Mogambery. (1991)
      This dissertation deals with the classification of varieties according to their Mal'cev properties. In general the so called Mal'cev-type theorems illustrate an interplay between first order properties of a given class ...
    • Southern African Large Telescope observations of Sunyaev-Zel'dovich effect selected clusters from the Atacama Cosmology Telescope. 

      Kirk, Brian. (2014)
      We present Southern African Large Telescope (SALT) follow-up observations of seven massive clusters detected by the Atacama Cosmology Telescope (ACT) using the Sunyaev-Zel’dovich effect (SZE). We conducted multi-object ...
    • Spatial modelling of fire dynamics in Savanna ecosystems. 

      Berjak, Stephen Gary. (1999)
      Fire is used in the management of ecosystems worldwide because it is a relatively inexpensive means of manipulating thousands of hectares of vegetation. Deciding how, where and when to apply fire depends primarily on the ...
    • The theory of option valuation. 

      Sewambar, Soraya. (1992)
      Although options have been traded for many centuries, it has remained a relatively thinly traded financial instrument. Paradoxically, the theory of option pricing has been studied extensively. This is due to the fact ...
    • Thermal evolution of radiation spheres undergoing dissipative gravitational collapse. 

      Reddy, Kevin Poobalan. (2015-09-04)
      In this study we investigate the physics of a relativistic radiating star undergoing dissipative collapse in the form of a radial heat flux. Our treatment clearly demonstrates how the presence of shear affects the collapse ...