Thesis (Ph. D.)--University of Washington, 1992. / Vita. Includes bibliographical references (leaves [146]-149).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 104-105).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Includes bibliographical references (p. 226-232).

This thesis begins by introducing the concept of a rigid quasilocal frame (RQF) as a geometrically natural way to define an extended system in the context of the dynamical spacetime of general relativity. An RQF is defined as a two-parameter family of timelike worldlines comprising the worldtube boundary of the history of a finite spatial volume with the rigidity conditions that the congruence of worldlines is expansion-free (the ``size'' of the system is not changing) and shear-free (the ``shape'' of the system is not changing). We demonstrate that this frame exists in flat and arbitrary curved spacetimes and, moreover, exhibits the full six motional time-dependent degrees of freedom we are familiar with from Newtonian mechanics. The latter result is intimately connected with the fact that a spatial slice through the RQF - having a two-sphere topology - always admits precisely six conformal Killing vector (CKV) fields (three boosts and three rotations) associated with the action of the Lorentz group on a two-sphere. These CKVs, along with the four-velocity of observers on the RQF, are then used to quasilocally define the energy, momentum, and angular momentum inside an RQF without relying on the pre-general relativistic practice of appealing to spacetime symmetries. These quasilocal definitions for energy, momentum, and angular momentum also involve replacing the local matter-only stress-energy-momentum (SEM) tensor with the Brown-York matter plus gravity boundary SEM tensor. This allows for the construction of completely general conservation laws which describe the changes in a system in terms of fluxes across the boundary. Furthermore, since an RQF is a congruence with zero expansion and shear only relevant fluxes appear in these conservation laws - that is, fluxes due merely to changes in the size or shape of the boundary are eliminated. These resulting fluxes are simple, exact, and quantified in terms of operationally-defined geometrical quantities on the boundary and we show that they explain at a deeper level the mechanisms behind gravitational energy and momentum transfer by way of the equivalence principle. In particular, when we accelerate relative to a mass, the energy changes at a rate proportional to our acceleration times the momentum (and we propose an exact gravitational analogue of the electromagnetic Poynting vector to capture this idea). Similarly, the momentum of that object changes at a rate proportional to our acceleration times the energy. This new insight has fascinating consequences for how we should understand everyday occurrences like a falling apple - that is, the change in energy of the apple involves frame dragging while the change in momentum involves extrinsic curvature effects near the apple. Our naive general relativistic intuition tells us that these quantities should be so tiny that they should be negligible and, indeed, they are tiny but they are multiplied by huge numbers to give rise to macroscopic effects. This is how general relativity universally explains the transfer of energy and momentum but we needed rigid quasilocal frames to uncover this beautiful property of nature. Using the RQF formalism we also investigate a variety of specific problems. In particular, while looking at time-dependent rotations we discover that the reason Ehrenfest's rigid rotating disk paradox has gone unsolved for so long is that rotation introduces a subtle non-locality in time. By this we mean that, in order to maintain rigidity while undergoing time-dependent rotation, one needs to know, not only the instantaneous rotation rate, but the entire history of the motion. This makes it impossible to keep a volume of observers rigid but is doable with an RQF. We also consider RQFs in the small-sphere limit to derive many of our results and one example with particularly interesting consequences involves Bell's spaceship accelerating through an electromagnetic field. Here, we show that the change in electromagnetic energy inside the spaceship is made up of two pieces: the usual electromagnetic Poynting flux accounts for half the change while the gravitational Poynting vector equally contributes to make up the other half. This means that electromagnetism in flat spacetime generically does not tell you what is actually going on. Rather, the curvature due to the electromagnetic field necessitates a fully general relativistic treatment to get the whole story. We also use the RQF linear momentum conservation law in the context of stationary observers and fields to derive, for the first time, an exact fully general relativistic analogue of Archimedes' law. In essence, this law demonstrates that the weight of the matter and gravitational fields contained in a finite region of space is supported by the stresses (buoyant forces) acting on the boundary of that region. Furthermore, in a post-Newtonian approximation, we derive a simple set of quasilocal conservation laws which describe non-relativistic systems bound by mutual gravitational attraction. In turn, we use these laws to obtain expressions for the rates of gravitational energy and angular momentum transfer between two tidally interacting bodies - that is, the tidal heating and tidal torque - without the need to define unphysical pseudotensors. Moreover, the RQF approach explains these transfers of energy and momentum again, not as the difference of forces acting on a tidal bulge, but instead more fundamentally in the language of the equivalence principle in terms of ``accelerations relative to mass''. Throughout this work we demonstrate that the RQF approach always gives very simple, geometrical descriptions of the physical mechanisms at work in general relativity. Given that this approach also includes both matter and gravitational energy, momentum, and angular momentum and does not rely on spacetime symmetries to define these quantities, we argue that we are seeing here strong evidence that the universe is actually quasilocal in nature. We are really deeply ingrained with a local way of thinking, so shifting to a quasilocal mindset will require great effort, but we contend that it ultimately leads to a deeper understanding of the universe.

Thesis (Ph. D.)--University of Notre Dame, 2008. / Thesis directed by Don Howard for the Department of History and Philosophy of Science. "July 2008." Includes bibliographical references (leaves 196-233).

Vacuum polarization by electric fields is a well established fact. Assuming that anti-matter has negative gravitational properties, the fluctating electric dipoles from the quantum vacuum may also have gravitational dipolar properties. A model is developed that describes how electric fields could gravitationally polarize the vacuum causing gravitational screening or anti-screening effects. This leads to a violation of the Weak Equivalence Principle or a general mass change most notabily for elementary particles, such as the electron or positron, below but close to measured boundaries. Also a gravitational vacuum torque is predicted to act on a charged capacitor perpendicular to a gravitational field. The predictions could be verified by future laboratory experiments that could contribute on our understanding of the gravitational properties of anti-matter.

Orientadores: Marcelo Moraes Guzzo e Pedro Cunha de Holanda. / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin. / Made available in DSpace on 2018-08-12T12:12:58Z (GMT). No. of bitstreams: 1 Valdiviesso_GustavodoAmaral_D.pdf: 2795816 bytes, checksum: 93e348ecdbd1623e5c6992f732c0af14 (MD5) Previous issue date: 2008 / Resumo: Neste trabalho, estudamos o modelo para violação do princípio da equivalência (VEP) em neutrinos solares e de reatores. Este modelo já foi considerado como uma solução promissora ao problema do neutrino solar (PNS), mas foi descartado por não ser capaz de explicar os dados referentes a neutrinos solares e anti-neutrinos de reatores, com um mesmo conjunto de parâmetros físicos. O modelo de mistura massa-sabor em conjunto com o efeito MSW tem se mostrado como único capaz de explicar todos os dados disponíveis na área. Novos limites para a violação do princípio da equivalência podem ser obtidos para neutrinos solares e de reatores, considerando agora um modelo combinado entre a hipótese de mistura massa-sabor e o modelo de VEP. Nossa análise mostra uma tendência favorável a duas soluções conjuntas onde os efeitos de VEP praticamente não alteram neutrinos solares: uma em que a escala de massa dos neutrinos de reatores permanece inalterada e outra onde tal escala cai levemente, se aproximando do resultado para o ajuste somente dos dados solares. A solução conjunta aponta para o seguinte conjunto de parâmetros: | f D g | = 9,12 + 0,97 -0,78 × 10-21, tan 2 q = 0,478 +0,040-0,038 e D m2 = 6,63 ± 0,31 × 10-5 eV 2 (77,7% C.L.) e | f D g | = 1,91+0,84 -0,61× 10-21, tan 2 q = 0,478+0,040-0,038 e D m2 = 7,73 +0,17-0,20 × 10-5 eV 2 (77,7% C.L.). Ambas soluções melhoram o nível de confiança com relação à solução MSW (tan2 q = 0,462+0,043-0,036 e D m2 = 7,75+0,16-0,12 x 10-5 eV2, 73,1% C.L.) Um limite superior para VEP foi obtido como sendo |f D g | £ 1,3 ×10-20(3 s ) sobre a solução MSW. / Abstract: In this work, we studied the model for the violation of the equivalence principle (VEP) on solar and reactor neutrinos. This model was already considered as a promising solution to the solar neutrino problem (SNP), but was abandoned because it wasn¿t able to explain all the data with a single set of physical parameters. The mass- avor mixing model, together with the MSW effect has been shown to as the only model able do explain all the available data. New limits for the VEP are obtained for solar and reactor neutrinos, considering a combined model, with the mass- avor mixing hypothesis and the VEP model. Our analysis shows two solutions were the VEP effects practically don¿t change the solar sector: one where the mass scale of the reactor sector remains the same and another one where this scale falls slightly, becoming closer to the solar solution. The combined solution points to the following set of parameters: a "higher vep" | f D g | = 9,12 + 0,97 -0,78 × 10-21, tan 2 q = 0,478 +0,040-0,038 and D m2 = 6,63 ± 0,31 × 10-5 eV 2 (77,7% C.L.) and a "lower vep" | f D g | = 1,91+0,84 -0,61× 10-21, tan 2 q = 0,478+0,040-0,038 e D m2 = 7,73 +0,17-0,20 × 10-5 eV 2 (77,7% C.L.). Both solutions increases the confidence level when compared with the MSW solution (tan2 q = 0,462+0,043-0,036 and D m2 = 7,75+0,16-0,12 x 10-5 eV 2, 73,1% C.L.) A superior limit has also been obtained for VEP: |f D g | £ 1,3 ×10-20(3 s ) over the MSW solution. / Doutorado / Física das Particulas Elementares e Campos / Doutor em Ciências

The equivalence principle has proven to be central to theories of gravity, with General Relativity being the simplest and most elegant theory to embody the principle. Most alternative theories of gravity struggle to satisfy the principle and still be distinct from GR. Extensions of cosmological and quantum theories question the irrefutably of the equivalence at every scale. The possibility of an equivalence principle violation at galactic scales would be an exciting prospect. In this thesis, we will carefully examine the equivalence principle through the study of chameleon scalar-tensor theories, this will include solutions for hypothetical stars known as boson stars. Such theories find varied application, especially in cosmology, where they model dark energy and inflation. The AWE hypothesis, is an instance of this. It is a nonuniversally coupled model in which violations of the equivalence principle on galactic scales may be apparent. We investigate spherically symmetric and static solutions within the framework of this theory. The constraints obtained from galactic rotation curves results in values of the couplings that show no significant violation of the equivalence principle or values consistent with a theory of dark energy

Durant ces deux dernières décennies, de nouvelles techniques pour refroidir et manipuler les atomes ont permis le développement de capteurs inertiels basés sur l'interférométrie atomique. Dans ce contexte, le projet ICE est basé sur l'utilisation d'un interféromètre atomique double espèce compacte et transportable dans le but de tester le principe d'équivalence faible. Nous comparons ainsi l'accélération de deux espèces chimiques et nous vérifions leur égalité en mesurant le paramètre d'Eötvös à un niveau de 10-6. Cette expérience a été réalisée en laboratoire et en micropesanteur lors de vols paraboliques à bord de l'Airbus A310 ZERO-G de Novespace. L'interféromètre est composé de deux échantillons de 87Rb et 39K refroidis par laser, possédant des longueurs d'onde de transitions atomiques similaires (780 nm et 767 nm) qui sont générées par un doublage de fréquence laser Télécom. Récemment, nous avons réalisé le premier interféromètre double espèce en micropesanteur. Cette expérience a ainsi permis le premier test du principe d'équivalence faible dans cet environnement en utilisant des objets quantiques, ce qui représente une première étape majeure vers une future mission spatiale. Dans le cadre de ces travaux, nous avons installé une source laser à 770 nm, accordée sur la transition D1 du 39K, afin de réaliser un refroidissement par mélasse grise. Nous avons également mis en place une nouvelle séquence pour préparer les atomes dans l'état mF = 0 avec une efficacité de transfert supérieure à 90%. Ces techniques ont amélioré le contraste de notre interféromètre de 39K d'un facteur 4, ce qui a mené à l'obtention d'une sensibilité sur le paramètre d'Eötvös dans le laboratoire de 5 x 10-8 après 5000 s d'intégration. / During the last two decades, new techniques to cool and manipulate atoms have enabled the development of inertial sensors based on atom interferometry. In this context, the ICE project is based on a compact and transportable dual-species atom interferometer in order to verify the weak equivalence principle (WEP). Thus, we compare the acceleration of two chemical species and verify their equality by measuring the Eötvös parameter at the 10-6 level.This experiment was performed both in the laboratory and in the microgravity environment during parabolic flights onboard the Novespace ZERO-G aircraft. The interferometer is composed of laser-cooled samples of 87Rb and 39K, which exhibit similar transition wavelengths (780 nm and 767 nm) derived from frequency-doubled telecom lasers. Recently, we have performed the first dual species interferometer in microgravity. This enables the first test of the WEP in weightlessness using quantum objects, which represents a major first step toward future mission in space.As part of these experiments, we have implemented a 770 nm laser source, resonant with the D1 transition of 39K, in order to perform a gray molasses cooling. We have also devised a new sequence to prepare atoms in the mF = 0 state with a transfer efficiency above 90%. These techniques improved the contrast of our 39K interferometer by a factor 4, which led to the obtention of a sensitivity on the Eötvös parameter in the laboratory of 5 x 10-8 after 5000 s of integration.

No / A heterogeneous hybrid computational electromagnetics method is presented, which enables different parts of an antenna simulation problem to be treated by different methods, thus enabling the most appropriate method to be used for each part. The method uses a standard frequency-domain moment-method program and a finite-difference time-domain program to compute the fields in two regions. The two regions are interfaced by surfaces on which effective sources are defined by application of the Equivalence Principle. An extension to this permits conduction currents to cross the boundary between the different computational domains. Several validation cases are examined and the results compared with available data. The method is particularly suitable for simulation of the behavior of an antenna that is partially buried, or closely coupled with lossy dielectric volumes such as soil, building structures or the human body.