Gravitational waves are predicted by Einstein’s general theory of relativity and have so far only been indirectly detected. The first direct detection should however only be a matter of time, with observatories across the world working hard to detect them. Once gravitational waves are detected they are predicted to be very useful in the field of astronomy. In order to be able to successfully interpret measurements from gravitational waves we need to have knowledge of how the wave is affected by its medium of propagation. Because of that, the purpose of this thesis is to investigate the behaviour of gravitational waves in the medium of a magnetised plasma. Using a kinetic plasma model, Einstein’s field equations and tetrad formalism, a general solution for a gravitational wave propagating in the medium is derived. The general solution is then used to find the dispersion relation of the gravitational wave for two special cases: the case of Alfvén resonance and the case of cyclotron resonance. The Alfvén case is already studied in the literature and is found to match the previous results saying it will not affect the wave much. The cyclotron resonance case is new and was chosen it can magnify the effects of the particles on the gravitational wave. The cases are studied with regards to detectability of a medium induced dispersion. The influence on the gravitational wave propagation is, however, found to be too small for dispersive effects to be detected in the cases studied / Gravitationsvågor förutses i Einsteins allmänna relativitetsteori och har så här långt endast blivit indirekt detekterade. Den första direkta detektionen är dock bara en tidsfråga och observatorier runtom i världen arbetar hårt för att lyckas med den. Då gravitationsvågor väl är detekterade sägs de ha stor potential inom astronomi. För att man ska kunna tolka mätdata från gravitationsvågor behöver man veta hur vågen beter sig i propagationsmediet. Av den anledningen är syftet med detta examensarbete att undersöka hur gravitationsvågor beter sig i ett magnetiserat plasma. Med hjälp av en modell för kinetisk plasma, Einsteins fältekvationer och tetradformalism härleds en allmän lösning för en gravitationsvåg som propagerar i en magnetiserad plasma fram. Lösningen används därefter för att hitta dispersionsrelationen för gravitationsvågen givet två specialfall: fallet för Alfvénresonans och fallet för cyklotronresonens. Alfvénfallet är redan studerat i tidigare litteratur och resultatet man hittar visar sig stämma överens med det tidigare funna resultatet som säger att det inte har en märkbar påverkan på vågen. Cyklotronresonansfallet är nytt och valdes eftersom att det kan förstärka de effekter som partiklarna har på gravitationsvågen. De båda specialfallen studeras närmare med avseende på detektion av en dispersion inducerad av mediet. Påverkan på gravitationsvågens propagation sluts dock till att vara för liten för att den ska bli uppmätt i de undersökta fallen.

This essay offers a deconstructive approach to Nabokov´s Lolita. Critics have tended to treat space and time as distinct concepts in the novel: choosing to analyse the role of either one or the other, and even when considering both, examining them in isolation. It´s narrator, Humbert Humbert, however, implies that "time" and "spatial" terms are interchangeable in a way reminiscent of Einstein´s Theory of Relativity in which space-time is a continuum that is experienced relative to the individual observer´s own position in the universe. This essay therefore explores the possibility that Nabokov may have used Einstein´s concept of space-time relativity as a metaphor in Lolita. The essay looks first at the various ways in which the idea of relativity surfaces throughout the novel not just in relation to space and time, but also in its moral, cultural and historic forms. The roles of the Hour Glass Lake, Lolita´s sunglasses and Humbert´s car, three of the novel´s chief symbols, are then discussed in relation to its key elements: the notion of time dilation, the place of the observer and Humbert´s space-time bubble. It next concentrates on how the characters in the novel exemplify the roles of both observer and observed in a modern, self-centred and morally relativistic world. The final section argues that Humbert’s "madness" represents the most extreme consequence of his living in his own solipsistic bubble of space-time, or "dream vacuum" as he calls it.

Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Jan. 5, 2010). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Physics, University of Alberta." Includes bibliographical references.

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

There is a debate in the philosophy of time over the status of non-present entities. Do these things exist, and if so, what sorts of things are they? Recently, the debate has split into two groups, presentists and eternalists. Presentists hold that no past or future things exist now. Socrates does not now exist, though he did in the past; my future daughter does not now exist, though she may in the future. Ontologically, the present is distinct, serving to demarcate all that currently has existence. As far as the eternalist is concerned, all entities - whether past, present, or future - are equally real. If it was, is, or will be, it can be found in the eternalist picture of time. As such, there is no distinct present at which some entities exist while others do not; rather, everything enjoys the same ontological status. I will be concerned to offer an assessment of the presentist view. Common objections against presentism will be examined, amplified, and answered where appropriate. I will not examine the arguments in favor of the presentist view. Rather, I wish to describe why it is that the eternalist feels compelled to deny presentism. Ultimately, my goal will be to show that although presentism survives some of the current objections raised against it, it does not survive them all. Presentism is an interesting, but ultimately unsatisfactory view. There is a modified form of presentism (call it presentism*) that can meet the objections raised against the original position, and after noting some of the objections raised against presentism, I will sketch the outlines of presentism* in some detail. I intend to show that presentism* is able to retain what is most valuable about presentism, while also withstanding certain objections that the latter view could not.

I investigate the self-force acting on static scalar and electric charges in Schwarzschild-de Sitter and Schwarzschild-Anti-de Sitter spacetimes. The self-force occurs when a charged particle's field interacts with the curvature of spacetime so that the particle interacts with its own field. Because the field of a point particle is singular at the location of the particle, it is necessary to decompose the field into a regular part responsible for the self-force and a singular part that does not contribute to the self-force. To do this, I use the mode-sum regularization scheme introduced by Barack and Ori, in which the field is decomposed into a sum over modes, and the singular part is removed from each mode using so-called regularization parameters. I find that the electrostatic self-force in Schwarzschild-de Sitter and Schwarzschild-Anti-de Sitter behaves similarly to Schwarzschild self-force near the black hole, but can deviate strongly at larger distances. This is especially true in Schwarzschild-Anti-de Sitter, where the self-force is seen to increase linearly with distance. I provide an explanation for this behaviour using conformal transformations. A particular feature evident in Schwarzschild-Anti-de Sitter is that the self-force can become negative (attractive) at small distances when the Schwarzschild radius and the cosmological length scale are of a similar order. I find that the scalar self-force in Schwarzschild-de Sitter can not actually be computed, and in Schwarzschild-Anti-de Sitter the asymptotic behaviour is similar to its electrostatic counterpart.

No description available.

In this thesis we seek exact solutions to the isotropic Einstien-Maxwell system that model the interior of relativistic stars. The field equations are transformed to a simpler form using the transformation of Durgapal and Bannerji (1983); the integration of the system is reduced to solving the condition of pressure isotropy. This condition is a recurrence relation with variable rational coe±cients which can be solved in general. New classes of solutions of linearly independent functions are obtained in terms of special functions and elementary functions for different spatial geometries. Our results contain models found previously including the superdense Tikekar (1990) neutron star model, the uncharged isotropic Maharaj and Leach (1996) solutions, the Finch and Skea (1989) model and the Durgapal and Bannerji (1983) superdense neutron star. Our general class of solutions also contain charged relativistic spheres found previously, including the model of Hansraj and Maharaj (2006) and the model of Thirukkanesh and Maharaj (2006). In addition, two exact analytical solutions describing the interior of a charged strange quark star are obtained by applying the MIT bag equation of state. We regain the Mak and Harko (2004) solution for a charged quark star as a special case. / Thesis (Ph. D.) University of KwaZulu-Natal, Westville, 2007.

In this thesis we study the conformal symmetries in two locally rotationally symmetric spacetimes and the homothetic symmetries of a Bianchi I spacetime. The conformal Killing equation in a class AIa spacetime (MacCallum 1980), with a G4 of motions, is integrated to obtain the general solution subject to integrability conditions. These conditions are comprehensively analysed to determine the restrictions on the metric functions. The Killing vectors are contained in the general conformal solution. The homothetic vector is obtained and the explicit functional dependence of the metric functions determined. The class AIa spacetime does not admit a nontrivial special conformal factor. We also integrate the conformal Killing equation in the anisotropic locally rotationally symmetric spacetime of class A3 (MacCallum 1980), with a G4 of motions, to obtain the general conformal Killing vector and the conformal factor subject to integrability conditions. The Killing vectors are obtained as a special case from the general conformal solution. The homothetic vector is found for a nonzero constant conformal factor. The explicit functional form of the metric functions is determined for the existence of this homothetic vector. The spatially homogeneous and anisotropic A3 spacetime also does not admit a nontrivial special conformal vector. In the Bianchi I spacetime, with a G3 of motions, the conformal Killing equation is integrated for a constant conformal factor to generate the homothetic symmetries. The integrability conditions are solved to determine the functional dependence of the three time-dependent metric functions. / Thesis (M.Sc.)-University of Natal, Durban, 1991.