Abstract . New models for a charged anisotropic star in general relativity are found. We consider a linear equation of state consistent with a strange quark star. In our models a new form of measure of anisotropy is formulated; our choice is a generalization of other pressure anisotropies found in the past by other researchers. Our results generalize quark star models obtained from the Einstein-Maxwell equations. Well-known particular charged models are also regained. We indicate that relativ...
Abstract In this mini thesis, we study the application of Lyapunov functions in epidemiological modeling. The aim is to give an extensive discussion of Lyapunov functions, and use some specific classes of epidemiological models to demonstrate the construction of Lyapunov functions. The study begins with a review of Lyapunov functions in general, and their usage in global stability analysis. Lyapunov’s “direct method” is used to analyse the stability of the disease-free equilibrium. More...
ABSTRACT We studied two models describing transmission dynamics of tuberculosis (TB) and discussed their implications to human health. The first model is analyzed in the presence of treatment of active TB persons and the screened asymptomatic TB infectives. The second model is analyzed by looking at treatment of drug sensitive TB as well as drug resistant TB individuals. The models are built with a motive to study the dynamical behaviors of the trajectories which has the potential to guide T...
Abstract Using the concept of parallel transport of vectors in curved manifolds, the Riemann curvature tensor in terms of Christoffel symbols is obtained. Making use of the Riemann curvature tensor’s symmetry properties, the Ricci curvature tensor and Einstein’s tensor are derived. Through Einstein’s tensor and the Poisson equation for Newtonian gravity, the Einstein field equations are introduced. Upon using Kerr metric (Kerr, 1963) as a solution for Einstein’s field equations, extra...
Abstract The Cape horse mackerel (Trachurus trachurus capensis ) has traditionally made an important contribution to the South African fishing industry and is a key component of the Benguela ecosystem. This thesis concerns the assessment and management of the South African horse mackerel resource. It starts with a brief review of the biology of the Cape horse mackerel and the history of the fishery, as well as of the Management Strategy Evaluation approach, which was applied in this work. Ass...
Abstract It is common to think of our universe according to the “block universe” idea, which says that spacetime consists of many “stacked” 3-surfaces varied as a function of some kind of proper time τ . Standard ideas do not distinguish past and future, but Ellis’ “evolving block universe” tries to make a fundamental distinction. One proposal for this proper time is the proper time measured along the timelike Ricci eigenlines, starting from the big bang. The main idea of this ...
Abstract In this thesis, we develop the 1 + 1 + 2 formalism, a technique originally devised for General Relativity, to treat spherically symmetric spacetimes in for fourth order theories of gravity. Using this formalism, we derive equations for a static and spherically symmetric spacetime for general f(R) gravity. We apply these master eqautions to derive some exact solutions, which are used to gain insight on Birkhoff's theorem in this framework. Additionally, we derive a covariant form of t...
Abstract The non-life insurance pricing consists of establishing a premium or a tariff paid by the insured to the insurance company in exchange for the risk transfer. A key factor in doing that is properly estimating the distribution that the claim and frequency of claim follows. This thesis aim at having a deep knowledge of loss function and their estimation, several concept from Measure Theory, Probability Theory and Statistics were combined in the study of loss function and estimating the...
Let us first introduce some keywords that will enable us to specify our principal objective. Given a nonempty set X and a function f : X → R which is bounded below, computing the number
Abstract Let X be a uniformly convex and uniformly smooth real Banach space with dual space X∗ . Let F : X → X∗ and K : X∗ → X be bounded monotone mappings such that the Hammerstein equation u + KF u = 0 has a solution in X. An explicit iteration sequence is constructed and proved to converge strongly to a solution of the equation. This is achieved by combining geometric properties of uniformly convex and uniformly smooth real Banach spaces recently introduced by Alber with our met...
This project is mainly focused on the theory of Monotone (increasing) Operators and its applications. Monotone operators play an important role in many branches of Mathematics such as Convex Analysis, Optimization Theory, Evolution Equations Theory, Variational Methods and Variational Inequalities.
ABSTRACT The study of variational inequalities frequently deals with a mapping F from a vector space X or a convex subset of X into its dual X 0 . Let H be a real Hilbert space and a(u, v) be a real bilinear form on H. Assume that the linear and continuous mapping A : H −→ H 0 determines a bilinear form via the pairing a(u, v) = hAu, vi. Given K ⊂ H and f ∈ H 0 . Then, Variational inequality(VI) is the problem of finding u ∈ K such that a(u, v − u) ≥ hf, v − ui, for all v ∈ ...
This body of work introduces exterior calculus in Euclidean spaces and subsequently implements classical results from standard Riemannian geometry to analyze certain differential forms on a manifold of reference, which here is a symmetric ellipsoid in R n . We focus on the foundations of the theory of differential forms in a progressive approach to present the relevant classical theorems of Green and Stokes and establish volume (length, area or volume) formulas. Furthermore, we introduce the ...
Abstract This thesis presents an overview on the theory of stopping times, martingales and Brownian motion which are the foundations of stochastic modeling. We started with a detailed study of discrete stopping times and their properties. Next, we reviewed the theory of martingales and saw an application to solving the problem of "extinction of populations". After that, we studied stopping times in the continuous case and finally, we treated extensively the concepts of Brownian motion and th...
ABSTRACT Let E be a 2-uniformly convex and uniformly smooth real Banach space with dual space E ∗ . Let A : C → E ∗ be a monotone and Lipschitz continuous mapping and U : C → C be relatively nonexpansive. An algorithm for approximating the common elements of the set of fixed points of a relatively nonexpansive map U and the set of solutions of a variational inequality problem for the monotone and Lipschitz continuous map A in E is constructed and proved to converge strongly.