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Browsing by Author "Dunsby, Peter K S"

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Beyond the concordance cosmology

Author: Gidelew, Amare Abebe Date: 2013 Includes abstract. Includes bibliographical references. Read more
Beyond the standard model of cosmology : a perturbative approach

Author: Osano, Bob Otieno Date: 2007 This thesis concerns higher order perturbations of the standard model of cosmology. The theme is addressed in two distinct research areas. The first area deals with linear perturbations of Bianchi type I model filled with dust whose flow is ... Read more
Cosmic electromagnetic fields due to perturbations in the gravitational field

Author: Mongwane, Bishop ; Dunsby, Peter K S ; Osano, Otieno Bob Date: 2012 We use non-linear gauge-invariant perturbation theory to study the interaction of an inflation produced seed magnetic field with density and gravitational wave perturbations in an almost Friedmann-Lemaˆıtre-Robertson-Walker (FLRW) spacetime ... Read more
Cosmological dynamics of exponential gravity

Author: Abdelwahab, Mohamed Elshazli Sirelakhatim Date: 2007 The objective of this thesis is to explore several hotly debated current issues in modern cosmology, with a focus on f(R) gravity. In chapter 1 we present a review of modern theoretical cosmology. We begin by introducing some fundamental ... Read more
A covariant approach to gravitational lensing

Author: De Swardt, Bonita Date: 2004 The main focus of this thesis is to study the properties of null geodesics in general relativistic models. This thesis is divided into two parts. In the first part, we introduce the (1+3)-covariant approach which will be used in our study of ... Read more
Covariant perturbations in f (R) - gravity of multi-component fluid cosmologies

Author: Gidelew, Amare Abebe Date: 2009 We study the evolution of scalar cosmological perturbations in the 1+3 Covariant Gauge-Invariant formalism for generic f(R) theories of gravity. Working in the energy frame of the total matter, we give a complete set equations describing the ... Read more
Exploring the cosmological dynamics of a viable theory for ƒ(R)-gravity

Author: Kandhai, Sulona Date: 2014 A viable theory for ƒ(R) gravity, the Hu-Sawicki (HS) model, is considered from a dynamical systems perspective. The case for which n=1, c₁=1 is treated, and qualitative information regarding the phase space of this model is extracted. Several ... Read more
Fluid and gas models in FLRW and almost FLRW universes

Author: Gebbie, Timothy John Date: 1996 Recently the universe has been modeled in the covariant sense, in terms of fluid models and perturbations thereof, leading to Gauge Invariant Covariant (GIC) perturbations of these fluid models. It is well known that kinetic theory provides ... Read more
General relativistic electrodynamics with applications in cosmology and astrophysics

Author: Betschart, Gerold Date: 2005 Includes bibliographical references. Read more
Problems in cosmology and numerical relativity

Author: Mongwane, Bishop Date: 2015 A generic feature of most inflationary scenarios is the generation of primordial perturbations. Ordinarily, such perturbations can interact with a weak magnetic field in a plasma, resulting in a wide range of phenomena, such as the parametric ... Read more
Review of current radiometer technology with suggestions for future South African satellites

Author: Calder-Potts, George Date: 2012 Given that South Africa is an emerging space nation, in a continent of emerging space nations and economies, several technologies need to be developed to progress the space program into a viable and sustainable endeavour. The three main areas ... Read more
A study of solutions and perturbations of spherically symmetric spacetimes in fourth order gravity.

Author: Nzioki, Anne Marie Date: 2013 In this thesis we use the 1+1+2 covariant approach to General Relativity to study exact solutions and perturbations of rotationally symmetric spacetimes in f(R) gravity, one of the most widely studied classes of fourth order gravity. We begin ... Read more
Tensors and Relativity Course

Author: Dunsby, Peter K S Date: 22 Aug 2014 This website contains lecture notes on Special and General Relativity, with a mathematical approach. The first part is exclusively dedicated to Special Relativity and its mathematical treatment using Tensors. The last four subjects go through ... Read more c b
Topics in contemporary cosmology

Author: Solomons, Deon Mark Date: 2003 Includes bibliographical references. Read more
Topics in cosmology

Author: Hobbs, Claudia Stacey Date: 2001 This thesis contains two distinct parts: the first part introduces and explains the relevant theory and background necessary for the analytic work done on magnetized cosmological perturbations at the end of the first part. The second part ... Read more
Topics in modified gravity

Author: Abdelwahab, Mohamed Elshazli Sirelakhatim Date: 2012 The key element of modern cosmology is the assumption that the General Theory of Relativity (GR) is the correct theory of gravitation. It replaced the Newtonian theory of gravity which was presented in the Principia in 1687. The fundamental ... Read more
Topics in stringy cosmology

Author: Goheer, Naureen Date: 2004 This thesis is composed of two distinct research topics. The first topic concerns Randall-Sundrum cosmological models, in particular their isotropization properties at early times. We first study the state space of inflationary braneworld ... Read more
Wavelet analysis of geomagnetic jerks

Author: de Wit, Tjaart Cornelis Date: 2013 Geomagnetic jerks, or secular variation impulses, are abrupt changes in the slope of the first time derivative of the Earth's magnetic field. These changes occur on time scales of the order of a year. It has been demonstrated that the jerks ... Read more