Metastable states are classically stable at zero temperature but can decay due to quantum tunneling. The rate of this process is exponentially small and it may be computed in Euclidean space in the Coleman-de Luccia formalism. The exponential suppression is determined by the Euclidean action computed on a trajectory with definite boundary conditions, known as Coleman-de Luccia instanton, or bounce. In some theories, the bounce may not exist or its on-shell action may be ill-defined or infinite, thus hindering the vacuum decay process. The issue of vacuum stability is, in fact, not just speculation: the Standard Model vacuum state is itself metastable. The Higgs field may tunnel outside its potential well, with catastrophic consequences for all observers. Luckily, the typical lifetime of such a state is predicted to be very long. Still, unknown high energy physics can change it by several orders of magnitude, and particle physics theories as well as cosmological models that predict large decay rates are ruled out thanks to the anthropic principle. Moreover, gravitational effects play an important role in this process, especially in the early Universe. It is thus important to examine in detail vacuum decay phenomena in gravitational settings and to keep the underlying field theory as general as possible. This thesis aims at exploring existence conditions for the Coleman-de Luccia instanton in gravitational settings. The first two chapters are dedicated to outlining the basic formalism and describing preexisting results about vacuum decay in cosmology. The Euclidean path integral approach for decay rate calculations, which was first discussed by Callan and Coleman, is introduced in Chapter 1. A quantum mechanical description of the problem is formulated and then extended to field theory. A detailed analysis of bounce calculations and their physical interpretation as bubbles of true vacuum follows. The Higgs field stability within the Standard Model is also addressed. Gravitational effects on the vacuum decay process are considered in Chapter 2, by focusing on the decay from Minkowski and de Sitter space, as they have important cosmological consequences respectively in the current Universe (due to the smallness of the cosmological constant) and at early times. The implications on Higgs decay are discussed in both settings. The last two chapters are dedicated to new results. Vacuum decay in field theories with a scalar field and quadratic gravity is investigated. An Einstein-Hilbert term, a non-minimal coupling, and a quadratic Ricci scalar are considered while keeping the scalar field potential general. The focus is on decay from Minkowski and de Sitter space, due to their importance in cosmology. Scalar fields with Einstein-Hilbert gravity are discussed in Chapter 3, by showing that the bounce at large Euclidean radii has an analytical form that is almost entirely independent of the potential, which is called the "asymptotic bounce". Bounds on the Hubble parameter in the de Sitter case are also explored, by giving an analytical explanation to numerical evidence present in the literature. These properties are used, in Chapter 4, to test for stabilization of the false vacuum state in quadratic gravity. Conclusions follow.

SILVA, Roger Ribeiro. Estudo das propriedades dielétricas do Niobato de Bismuto e Titânio dopado com PbO e Bi2O3 para aplicações em antenas. 2009. 93 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2009. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-06-16T21:40:35Z No. of bitstreams: 1 2009_dis_rrsilva.pdf: 3731493 bytes, checksum: ea1e0ca9dd5b082cce643034649ad572 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-06-18T18:22:11Z (GMT) No. of bitstreams: 1 2009_dis_rrsilva.pdf: 3731493 bytes, checksum: ea1e0ca9dd5b082cce643034649ad572 (MD5) / Made available in DSpace on 2015-06-18T18:22:11Z (GMT). No. of bitstreams: 1 2009_dis_rrsilva.pdf: 3731493 bytes, checksum: ea1e0ca9dd5b082cce643034649ad572 (MD5) Previous issue date: 2009 / Dielectric resonators based on type structure compound Bi3TiNbO9 show singular characteristics for microwave applications, including high dielectric constants, low dissipation losses and low temperature coefficients. Single phase of the Bi3TiNbO9 powder was obtained by x-ray diffraction technique. The ceramics doped during manufacture, with lead oxide and bismuth oxide, were synthesized by solid state reaction at 950°C for two hours. Samples were analysed by Archimedes method and exhibited good levels of density for doped ceramics with bismuth and lead oxide. Grain morphology and stoichiometry of ceramics were investigated by scanning electron microscopy and energy dispersive spectroscopy technique. Far infrared spectroscopy identified large bands on the Bi3TiNbO9 structure by attenuated total reflection technique. Radiofrequency measurements showed that doped ceramics exhibited higher dielectric constants than pure phase. Microwave measurements were investigated by Hakki-Coleman and resonant cylindrical cavity. The ceramics called as BTNO3BiP, BTNO5BiP, BTNO10BiP, BTNO3PbG e BTNO5PbG, showed high dielectric constants and high quality factors demonstrating that they can be applied in dielectric antennas on microwave range. / Ressoadores dielétricos baseados na estrutura do composto Bi3TiNbO9 apresentam características singulares para aplicações em microondas, incluindo altas constantes dielétricas, baixos fatores de dissipação e baixos coeficientes de temperatura. Obteve-se a fase pura da amostra em pó de Bi3TiNbO9 pela técnica de difração de raios X. As amostras cerâmicas dopadas durante a fabricação, com óxido de chumbo e óxido de bismuto, foram sintetizadas pelo método de reação do estado sólido a 950°C por 2 horas. As amostras foram analisadas pelo método de Arquimedes e apresentaram bons níveis de densidade nas dopagens com os óxidos de bismuto e chumbo. A morfologia dos grãos e a estequiometria das amostras cerâmicas foram investigadas pelas técnicas de microscopia eletrônica de varredura e análise por energia dispersiva de raios X. A espectroscopia no infravermelho distante identificou bandas largas na estrutura do Bi3TiNbO9 pela técnica de reflexão total atenuada. As medidas de constante dielétrica e perda dielétrica em radiofreqüência demonstraram que as dopagens com chumbo e bismuto exibiram maiores constantes dielétricas em relação à cerâmica pura. As medidas em microondas foram estudadas pelos métodos Hakki-Coleman e a cavidade ressonante metálica. As cerâmicas denominadas como BTNO3BiP, BTNO5BiP, BTNO10BiP, BTNO3PbG e BTNO5PbG, apresentaram altas constantes dielétricas e altos fatores de qualidade, demonstrando que podem ser aplicadas em antenas dielétricas na faixa de micro-ondas.

This thesis investigates the management of social capital processes as they are accomplished-understood, experienced and shaped-by owner-managers. The aim of the thesis is to develop a deeper understanding of the management of social capital processes, to achieve a greater congruence between real-life perspectives and experiences and social capital literature. The thesis argues that social capital is situational, and in the economic situation the theory has been bounded by rational choice framing assumptions. The research problem is that claims for the universality of the economic way of looking at life, and for looking at social capital processes are over-stated. Predicated on this insight the research investigates economic notions of rationality, and low and non-rationality, as well as their inter-dependence in the management of social capital processes. The research follows a qualitative approach for data collection, with flexible pre-coding to guide the research where to look, while retaining an inductive openness to emergent data. The research population is drawn from SME owner-managers in the service and retail sectors, who were researched over two years using semi-structured interviews, observation, and by researcher participant observation. The thesis presents a number of contributions to knowledge. First, the thesis offers an in-depth, single source review explicating the meaning of the economic form of social capital, with reference to its intellectual antecedents, conceptual debates and key theoretical authors. The second (emergent research) contribution is to identify the significance of ethics and autodidactic reading for managing social capital processes. The third (theoretical) contribution argues for an expanded social capital perspective, beyond the prevailing and over-confident rational framing assumptions, and also for a new holistic ontological understanding. The fourth contribution is to identify a number of generic processes which can guide the management of social capital processes.

The consequences of mine seismicity can be mitigated by installing support systems capable of absorbing the energy generated by seismic events. Recent work has focused on the testing of individual support or reinforcement units under laboratory impact loads; this, however, does not render itself to easy extrapolation to field conditions. Hence, this thesis focuses on improving the understanding of the performance of support systems in real-world applications through passive monitoring of past rockburst events. 14 years of rockburst history were collected from Coleman Mine and Copper Cliff Mine, two of Vale’s underground (nickel) operations in Sudbury Ontario. Statistical analysis, principal component analysis (PCA) and partial least square projection (PLS) were utilized to find relation between collected parameters and performance capacity. This thesis discusses the adequacy of various support systems and investigates the validity of perceived support performance as compared to the actual performance based on analyses of field data.

The consequences of mine seismicity can be mitigated by installing support systems capable of absorbing the energy generated by seismic events. Recent work has focused on the testing of individual support or reinforcement units under laboratory impact loads; this, however, does not render itself to easy extrapolation to field conditions. Hence, this thesis focuses on improving the understanding of the performance of support systems in real-world applications through passive monitoring of past rockburst events. 14 years of rockburst history were collected from Coleman Mine and Copper Cliff Mine, two of Vale’s underground (nickel) operations in Sudbury Ontario. Statistical analysis, principal component analysis (PCA) and partial least square projection (PLS) were utilized to find relation between collected parameters and performance capacity. This thesis discusses the adequacy of various support systems and investigates the validity of perceived support performance as compared to the actual performance based on analyses of field data.

Dans ce travail, je propose une transition des théories de l'art relationnelles de Danto et Zangwill vers une conception évolutionniste et esthétique de l'art. Je souligne l'importance de conserver le point fort de ces théories relationnelles, soit leur prise en compte de l'intentionnalité. Il faudrait cependant naturaliser cette notion. Partant de la théorie de Danto, j'expose sa conception, fondée sur le cas des paires d'objets indiscernables. Ceux-ci remettent l'importance de l'esthétique en question en théorie de l'art. Parce que deux objets perceptuellement identiques peuvent avoir des statuts radicalement différents, il semblerait que les propriétés esthétiques ne jouent pas de rôle de premier plan en art. Danto propose que l'intentionnalité, le fait d'avoir un propos, constitue l'élément distinct de l'art. Cependant, sa théorie repose sur la notion d'identification artistique, elle-même tributaire d'une conception du fonctionnement des processus neuronaux que je rejette. Poursuivant ma critique de Danto, j'aborde Nick Zangwill, qui accepte l'intentionnalité comme essence de l'art, mais critique le rôle joué par le public, un autre point déterminant dans la théorie de Danto. Zangwill souhaite développer une théorie esthétique de l'art centrée sur l'aperçu esthétique et l'autonomie de l'artiste vis-à-vis des influences extérieures. Cependant, cette autonomie repose sur un argument de principe dont il ne fournit pas de preuves empiriques, et qui demeure vulnérable vis-à-vis un certain type d'argument sociologique émis par Fowler. De plus, des difficultés surviennent lorsque l'on tente de spécifier les motivations qui poussent à l'activité artistique dans les théories conceptuelles de Danto et Zangwill. J'explore par la suite un certain nombre d'autres critiques émises par Margolis à l'endroit de Danto. Je plaide en faveur de la naturalisation de plusieurs concepts importants pour la théorie de l'art, dont la notion d'identification. Je soutiens qu'une approche évolutionniste aurait l'avantage d'offrir des pistes de solutions quant à l'intérêt que nous prenons à l'activité artistique, en rapportant celle-ci à nos conditions d'existence. Je propose enfin la notion d'instinct esthétique, afin de prendre en compte de nombreux aspects liés à l'évolution de la perception et qui n'étaient pas suffisamment explicités dans les théories évolutionnistes de Miller ou de Wilson. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Danto, Zangwill, intentionnalité, esthétique, évolution

No description available.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [240]-248).

Thesis (M.A.)--Lancaster Bible College, 2003. / Includes bibliographical references (leaves 83-85).

Thesis (M.A.)--Lancaster Bible College, 2003. / Includes bibliographical references (leaves 83-85).