Dissertations / Theses on the topic 'Spacelink'

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
Dado um espaÃo-tempo M─n+1 = I x à Fn Robertson-Walker generalizado onde à à a funÃÃo warping que verifica uma certa condiÃÃo de convexidade, vamos classificar hipersuperfÃcies tipo-espaÃo fortemente estÃveis com curvatura mÃdia constante. Mais precisamente, vamos mostrar que, considerando x : Mn→ M─n+1 uma hipersuperfÃcie tipo-espaÃo fortemente estÃvel, fechada imersa em M─n+1 com curvatura mÃdia constante H, se a funÃÃo warping à satisfaz Ãâ ≥ max {H Ãâ, 0} ao longo de M, entÃo Mn à maximal ou uma folha tipo-espaÃo Mto={to} x F, para algum to Є I.
Give a generalized M─n+1 = I xà Fn Robertson-Walker spacetime whose warping function verifies a certain convexity condition, we classify strongly spacelike hypersurfaces with constant mean curvature. More precisely, we will show that given x : Mn → M─n+1 a closed, strongly stable spacelike hypersurfaces of M─n+1 with constant mean curvature H, if the warping function à satisfying à ≥ max {HÃ', 0} along M, is either maximal or a spacelike slice Mto = {to} x F, for some to Є I.

The object of study are complete spacelike hypersurfaces in a generalized Robertson-Walker spacetime. We make use of a new local form of the weak maximum principle for a class of operators including the Lorentzian mean curvature operator in order to obtain some mean curvature estimates and height estimates for spacelike hypersurfaces. These estimates are related to some rigidity results. We also give height estimates for spacelike hypersurfaces with constant higher order mean curvature, which are obtained via the local form of the weak maximum principle for an appropriate class of operators.

In this thesis we are going to investigate the behaviour of geodesics in a metric with a singularity known as the ``Mixmaster Universe''. This was motivated from previous work done, where the now well-known AdS/CFT correspondence was used to extract information about an AdS Schwarzschild black hole singularity beyond the horizon by studying correlators on the boundary that correspond to spacelike geodesics which bounce off the singularity. It was then shown that when the singularity was a cosmological one (in this case a Friedmann Robertson Walker cosmology with a Big Crunch), this was no longer possible as it is impossible for spacelike geodesics to bounce off this kind of singularity. This raises the question of whether, when an example of a more general singularity (the ``Mixmaster Universe'') is considered, it is possible for the spacelike geodesics to bounce away from this kind of singularity. This would enable us to potentially extract information about the singularity from the boundary correlators. Unfortunately, it will be shown that bouncing of such geodesics is extremely unlikely (if not impossible) and thus we would be unable to extract information about the singularity in the mixmaster universe using such a technique. We also discuss another aspect of the evolution of the mixmaster universe which shows that it does indeed have a very complicated evolution.

Approved for public release; distribution is unlimited
In 2001, the Air Force issued AFSPC 001-01, Mission Need Statement for Operationally Responsive Spacelift, identifying the need for a responsive launch system ready to launch and reach orbit within hours of call-up to deploy space assets in support of military operations. Current range operations include months and often years of pre-launch planning and infrastructure development in order to meet launch vehicle, customer, and safety constraints. This thesis studies the Air Forces limited ability to support small satellite launches into sun-synchronous low earth orbit in response to a Tier-2 ORS request, focusing on launching from a single range with two different small payload launch vehicles and investigates the potential for making spacelift more responsive. This investigation determined that the Air Force is not currently capable of launching either vehicle type within a seven day schedule due to a variety of doctrinal, procedural, and resource challenges and restrictions. This thesis presents several suggested changes and risk mitigation options for overcoming these shortfalls in equipment, personnel, and paperwork to increase the responsiveness of spacelift in support of the Air Force and DoD launch objectives.

Einstein's equations in vacuum spacetimes with two spacelike killing vectors are explored using affine projection tensor geometry. By doing a semi-conformal transformation on the metric, a new "fiducial" geometry is constructed using a projection tensor fields. This fiducial geometry provides coordinate independent information about the underlying structure of the spacetime without the use of an explicit form of the metric tensor.

Two main results are proved. The first is for the maximal graph system in semi-Euclidean spaces. Existence of smooth solutions to the Dirichlet problem is proved, under certain assumptions on the boundary data. These assumptions allow the application of standard elliptic PDE methods by providing sufficiently strong a priori gradient estimates. The second result is a version of Brian White’s local regularity theorem, but now for the spacelike mean curvature flow system in semi-Euclidean spaces. This is proved using a version of Huisken’s monotonicity formula. Under the assumption of a suitable gradient bound, this theorem will give a priori estimates that allow such flows to be smoothly extended locally.

Thesis (M.S. in Systems Engineering)--Naval Postgraduate School, September 2008.
Thesis Advisor(s): Osmundson, John S. ; Huynh, Thomas V. "September 2008." Description based on title screen as viewed on November 3, 2008. Includes bibliographical references (p. 63-64). Also available in print.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada
The Spacelift Range infrastructure of the United States Air Force will, over the next decade, experience a major modernization and upgrade. The goal of the Range Standardization and Automation (RSA) Program is to meet the requirements of range users and range safety in a more cost effective manner than is currently possible. One approach that will be considered in best achieving these goals is the further application of GPS technology to both the Eastern and Western Spacelift Ranges. Such an application can have a profound impact on the instrumentation segment of each range. Included within the instrumentation segment and clearly impacted, are both the metric tracking and telemetry subsystems. This paper considers the SLRS requirements that can be supported with GPS technology; the advantages and shortcomings of both GPS technology and alternative techniques; and provides suggestions as to an appropriate application of GPS technology to the SLRS.

The Hockney - Falco Thesis (THFT) refers to findings published by the artist, David Hockney, and his fellow collaborator, Dr. Charles M. Falco, University of Arizona Professor of Optical Sciences. THFT builds upon Hockney's theories first published in his book, Secret Knowledge: Rediscovering the Lost Techniques of the Old Masters (2001, 2006), by further demonstrating how some Renaissance artists including, van Eyck, Lotto, and Caravaggio, used optics as tools for creating works of art.This arts-based case study reveals that Hockney and Falco's discoveries were significantly informed by their respective practices of art and imaging, and demonstrates why Falco's experiences with Hockney, specifically, has and continues to influence his scientific research practice. These findings support Sullivan's (2004, 2005, 2006) theory of art-practice as research and demonstrate that THFT has significant implications for research and instruction of art and visual culture education.

Asymptotically flat spaces are widely studied because it is one natural way of describing an isolated system in general relativity. In this thesis we study what happens to the Lanczos potential at spacelike infinity in such spacetimes. By transformations of the Weyl-Lanczos equation, we derive expressions for the limiting equations on both the timelike unit hyperboloid, and the timelike unit cylinder. Finally the Newman-Penrose formalism is used to get a component version of the equations.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
Este trabalho tem como objetivo fornecer uma caracterizaÃÃo de hipersuperfÃcies tipo espaÃo completas no espaÃo anti de Sitter, tais como os cilindros hiperbÃlicos, sob a hipÃtese de curvatura mÃdia constante e duas curvaturas principais distintas. No caso em que umas das curvaturas principais à simples, à adicionada uma condiÃÃo sobre tais curvaturas. A caracterizaÃÃo aqui sugerida, teve como refrÃncia principal o trabalho de B. Yang e X. Liu, que dà uma resposta positiva à conjectura de L. F. Cao e G. Wei sobre hipersuperfÃcies tipo espaÃo em tais condiÃÃes. Para a realizaÃÃo do trabalho, foi utilizada uma fÃrmula do tipo Simons juntamente com o PrincÃpio do MÃximo Generalizado (Omori-Yau).
The aim of this work is to provide a characterization complete spacelike hypersurfaces in anti de Sitter space, such as hyperbolic cylinders, under the assumption constant mean curvature and two distinct principal curvatures. In the case that one of the principal curvatures is simple, a condition is added on the curvature. The characterization suggested here had as main reference the work of B.Yang and X. Liu, giving a positive answer to the L. F. Cao and G. Weiâs conjecture on spacelike hypersurfaces in such conditions. To carry out the work, we used a formula of type Simons along with the Generalized Maximum Principle (Omori-Yau).

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada
This paper will investigate the areas which must be addressed to implement a truly integrated Range instrumentation system on a GPS-based Range, using a patented L-Band commanding scheme. Hardware issues will be highlighted as well the issues to be addressed in changing from an audio tone-frequency modulated command system to a digital system incorporating encryption and spread spectrum. Some thoughts addressing costs and schedule to incorporate this approach into the architecture of the U. S. Air Force Range Standardization and Automation (RSA) architecture, as a candidate GPS-based Range are also presented, as well as a discussion of the benefits to be accrued over the existing system, if this approach were adopted.

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Neste trabalho, apresentamos um estudo das hipersuperfícies tipo-espaço imersas no ambiente −R × Hn, exibindo condições para que tais hipersuperfícies sejam slices {t0}×Hn. Para uma melhor compreensão das demonstrações e dos resultados, inserimos processos de diferenciação, cálculos de gradientes e Laplacianos que, juntamente com o princípio do máximo de Omori-Yau, foram cruciais no desenvolvimento dos resultados que, em sua maioria são do tipo Bernstein. Também incluímos um resultado do tipo Calabi.
In this work we present a study of the spacelike hypersurfaces immersed in the manifold −R × Hn providing sufficient conditions for such hypersurfaces be slices, {t0}×Hn. For a better understanding of the proofs and results, we have added differentiation processes, gradient computations and Laplacians which jointly with the Omori-Yau Maximum Principle were crucial in the developing of the results whose are mostly Bernstein-type. In the elapsing we also included Calabi-type results.

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Capes
Neste trabalho, como uma aplicação adequada do bem conhecido Princípio do Máximo Generalizado de Omori-Yau, obtemos resultados relativos a rigidez para hipersuperfícies tipo-espaço completas imersas na metade Hn+1 do espaço de De Sitter Sn+11 , que é chamado de steady state space. Por outro lado, usando uma isometria equivalente para o modeloHn+1, estenderemos nossos resultados a uma família maior de espaços-tempos. Por fim, estudaremos também a singularidade de gráficos verticais inteiros nesses espaços-tempos ambiente.
In this work, as a suitable application of the well known generalized Maximum Principle of Omori-Yau, we obtain rigidity results concerning to complete spacelike hypersurfaces immersed in the half Hn+1 of the de Sitter spaceSn+11 , which models the so-called steady state space. Moreover, by using an isometrically equivalent model for Hn+1, we extend our results to a wider family of spacetimes. Finally, we also study the uniqueness of entire vertical graphs in such ambient spacetimes.

Parmi les motivations pour une théorie au-delà du Modèle Standard (MS) de la physique des particules, l'existence de nouvelles échelles au-dessus du TeV pose la question de la stabilité de l'échelle électrofaible au travers des corrections radiatives à la masse du boson de Higgs. Une voie attrayante pour protéger l'échelle électrofaible est de construire des scenarii avec q Dimensions Spatiales Supplémentaires (DSS) compactifiées sur un tore où l'échelle de gravité à (4+q)D est ramenée au TeV, grâce à un grand volume compactifié, et agit comme une échelle de coupure pour le MS. Ces modèles souffrent d'un problème de stabilisation des grands rayons de compactification. Dans l'autre paradigme avec une petite DSS courbe, le champ de Higgs est en général localisé sur un bord de la DSS (TeV-brane) où l'échelle de gravité y est ramenée au TeV par un facteur de courbure. Si les bosons de jauge et les fermions du MS se propagent dans la DSS courbe, on peut générer la hiérarchie de masse des fermions. Il est donc crucial de traiter soigneusement les masses localisées sur la TeV-brane pour de tels fermions, ce qui est fait dans la littérature par une procédure de régularisation manquant de rigueur et surtout s'avérant inutile, comme nous le démontrons en détails dans cette thèse. La première phase de la thèse est dédiée au traitement de termes de masse localisés pour les fermions à 5D, ce qui implique d'introduire de nouveaux termes dans le lagrangien aux bords de la DSS courbe, analogues aux termes de Gibbons-Hawking en gravité. La deuxième phase consiste en une application de différentes méthodes (champs fonctions/distributions, calculs 4D/5D, etc) à divers termes branaires (termes cinétiques, masses de Majorana, etc), ainsi qu'en une généralisation à plusieurs modèles (dimensions plates/courbes, intervalle/orbifold, etc) classifiés. Dans une troisième phase, nous proposons de compactifier une DSS plate sur un graphe étoile/rose avec un grand nombre de petites branches/pétales identiques. On obtient un espace compactifié avec un grand volume sans une grande longueur de compactification à stabiliser. On utilise l'approche des fermions à 5D pour construire un modèle jouet de petites masses de Dirac pour les neutrinos (neutrinos gauches branaires et droits dans le bulk)
Among the motivations for a theory beyond the Standard Model (SM) of particle physics, the existence of new scales above the TeV implies the question of the stability of the electroweak scale with respect to radiative corrections to the Higgs boson mass. An attractive way to protect the electroweak scale is to build scenarii with q Spacelike Extra Dimensions (SED) compactified on a torus where the (4+q)D gravity scale is reduced to the TeV, through a large compactified volume, and acts as a cut-off for the SM. These models suffer from a problem of stabilization of the large compactification radii. Within the other paradigm with a small warped SED, the Higgs field is in general localized at a boundary of the SED (TeV-brane) where the gravity scale is redshifted to the TeV by a warp factor. If the SM gauge bosons and fermions propagate into the warped SED, one can generate the mass hierarchy for fermions. It is thus crucial to treat carefully the TeV-brane localized masses for such fermions, which is done in the literature by applying a regularization process suffering from a lack of consistency and more importantly being useless, as we demonstrate in detail in the present thesis. The first part of the thesis is devoted to the treatment of brane localized mass terms for 5D fermions, which requires the introduction of new Lagrangian terms at the SED boundaries, similar to the Gibbons-Hawking terms in gravity. The second part consists in applying different methods (function/distribution fields, 4D/5D calculations, etc) to various brane localized terms (kinetic terms, Majorana masses, etc), as well as a generalization to several classified models (flat/warped dimensions, intervalle/orbifold, etc). In the third part, we propose to compactify a flat SED on a star/rose graph with a large number of identical small leaves/petals. We obtain a compactified space with a large volume without a large compactification length to stabilize. We use the approach of 5D fermions to build a toy model of small Dirac neutrino masses (brane localized left-handed neutrinos and bulk right-handed ones)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Our purpose is to study the geometry of Riemannian immersions in certain semi- Riemannian manifolds. Initially, considering linearWeingarten hypersurfaces immersed in locally symmetric manifolds and, imposing suitable constraints on the scalar curvature, we guarantee that such a hypersurface is either totally umbilical or isometric to a isoparametric hypersurface with two distinct principal curvatures, one of them being simple. In higher codimension, we use a Simons type formula to obtain new characterizations of hyperbolic cylinders through the study of submanifolds having parallel normalized mean curvature vector field in a semi-Riemannian space form. Finally, we investigate the rigidity of complete spacelike hypersurfaces immersed in the steady state space via applications of some maximum principles.
Nos propomos estudar a geometria de imersões Riemannianas em certas variedades semi-Riemannianas. Inicialmente, consideramos hipersuperfícies Weingarten lineares imersas em variedades localmente simétricas e, impondo restrições apropriadas à curvatura escalar, garantimos que uma tal hipersuperfície é totalmente umbílica ou isométrica a uma hipersuperfície isoparamétrica com duas curvaturas principais distintas, sendo uma destas simples. Em codimensão alta, usamos uma fórmula do tipo Simons para obter novas caracterizações de cilindros hiperbólicos a partir do estudo de subvariedades com vetor curvatura média normalizado paralelo em uma forma espacial semi-Riemanniana. Finalmente, investigamos a rigidez de hipersuperfícies tipo-espaço completas imersas no steady state space via aplicações de alguns princípios do máximo.

In this paper, we study Bézier surfaces in View the MathML source three-dimensional Minkowski space. In particular, we focus on timelike and spacelike cases for Bézier surfaces. We also deal with the Plateau¿Bézier problem in View the MathML source, obtaining conditions over the control net to be extremal of the Dirichlet function for both timelike and spacelike Bézier surfaces. Moreover, we provide interesting examples showing the behavior of the Plateau¿Bézier problem in View the MathML source and illustrating the relationship between it and the corresponding Plateau¿Bézier problem in the Euclidean space R3.