The thesis deals with the issue of measuring the height of the center of gravity of SUV´s. The first part of thesis is devoted to the issue of center of gravity and the influence of the height of the center of gravity on driving stability. Furthermore, individual methods of measuring the height of the center of gravity in passenger cars are discussed. The analytic part of the thesis is devoted to experimental measurement of the height of the center of gravity of selected SUV´s at different vehicle load, by the method of tilting the vehicle on the axle. The results of the measurements showed that the height of the center of gravity for vehicles with a capacity for five people is in the range from 606 to 697 mm. The lowest value belongs to the vehicle Toyota RAV4 Hybrid, when loaded by the driver. The highest value was found for the vehicle Kia Sportage, when loaded by three passengers. The Landover Defender, which is vehicle, that has a capacity for nine people, was found to have a height of center of gravity ranging from 705 to 874 mm. The lowest value was found when loaded by the driver, the highest value when loaded by nine passengers. Only for the Nissan Qashqai was the growing dependence between the load increase and the height position of the vehicle's center of gravity confirmed. A similar trend was found for the Toyota RAV4 Hybrid, Jeep Compass and Landover Defender. The determined values can be used in the analysis of traffic accidents of SUV’s.

In einigen Ansätzen zu einer Quantentheorie der Gravitation wie Gruppenfeldtheorie und Schleifenquantengravitation zeigt sich, dass Zustände und Entwicklungen der geometrischen Freiheitsgrade auf einer diskreten Raumzeit basieren. Die dringendste Frage ist dann, wie die glatten Geometrien der Allgemeinen Relativitätstheorie, beschrieben durch geeignete geometrische Beobachtungsgrößen, aus solch diskreten Quantengeometrien im semiklassischen und Kontinuums-Limes hervorgehen. Hier nehme ich die Frage geeigneter Beobachtungsgrößen mit Fokus auf die effektive Dimension der Quantengeometrien in Angriff. Dazu gebe ich eine rein kombinatorische Beschreibung der zugrunde liegenden diskreten Strukturen. Als Nebenthema erlaubt dies eine Erweiterung der Gruppenfeldtheorie, so dass diese den kombinatorisch größeren kinematischen Zustandsraum der Schleifenquantengravitation abdeckt. Zudem führe ich einen diskreten Differentialrechnungskalkül für Felder auf solch fundamental diskreten Geometrien mit einem speziellen Augenmerk auf dem Laplace-Operator ein. Dies ermöglicht die Definition der Dimensionsobservablen für Quantengeometrien. Die Untersuchung verschiedener Klassen von Quantengeometrien zeigt allgemein, dass die spektrale Dimension stärker von der zugrunde liegenden kombinatorischen Struktur als von den Details der zusätzlichen geometrischen Daten darauf abhängt. Semiklassische Zustände in Schleifenquantengravitation approximieren die entsprechenden klassischen Geometrien gut ohne Anzeichen für stärkere Quanteneffekte. Dagegen zeigt sich im Kontext eines allgemeineren, auf analytischen Lösungen basierenden Modells für Zustände, die aus Überlagerungen einer großen Anzahl von Komplexen bestehen, ein Fluss der spektralen Dimension von der topologischen Dimension d bei kleinen Energieskalen hin zu einem reellen Wert zwischen 0 und d bei hohen Energien. Im Spezialfall 1 erlauben diese Resultate, die Quantengeometrie als effektiv fraktal aufzufassen. / In several approaches towards a quantum theory of gravity, such as group field theory and loop quantum gravity, quantum states and histories of the geometric degrees of freedom turn out to be based on discrete spacetime. The most pressing issue is then how the smooth geometries of general relativity, expressed in terms of suitable geometric observables, arise from such discrete quantum geometries in some semiclassical and continuum limit. In this thesis I tackle the question of suitable observables focusing on the effective dimension of discrete quantum geometries. For this purpose I give a purely combinatorial description of the discrete structures which these geometries have support on. As a side topic, this allows to present an extension of group field theory to cover the combinatorially larger kinematical state space of loop quantum gravity. Moreover, I introduce a discrete calculus for fields on such fundamentally discrete geometries with a particular focus on the Laplacian. This permits to define the effective-dimension observables for quantum geometries. Analysing various classes of quantum geometries, I find as a general result that the spectral dimension is more sensitive to the underlying combinatorial structure than to the details of the additional geometric data thereon. Semiclassical states in loop quantum gravity approximate the classical geometries they are peaking on rather well and there are no indications for stronger quantum effects. On the other hand, in the context of a more general model of states which are superposition over a large number of complexes, based on analytic solutions, there is a flow of the spectral dimension from the topological dimension d on low energy scales to a real number between 0 and d on high energy scales. In the particular case of 1 these results allow to understand the quantum geometry as effectively fractal.

No description available.

In this study we investigate the interactions between two co-rotating vortices. These vortices are subject to rapid rotation and stable stratification such as are found in planetary atmospheres and oceans. By conducting a large number of simulations of vortex interactions, we intend to provide an overview of the interactions that could occur in geophysical turbulence. We consider a wide parameter space covering the vortices height-to-width aspect-ratios, their volume ratios and the vertical offset between them. The vortices are initially separated in the horizontal so that they reside at an estimated margin of stability. The vortices are then allowed to evolve for a period of approximately 20 vortex revolutions. We find that the most commonly observed interaction under the quasi-geostrophic (QG) regime is partial-merger, where only part of the smaller vortex is incorporated into the larger, stronger vortex. On the other hand, a large number of filamentary and small scale structures are generated during the interaction. We find that, despite the proliferation of small-scale structures, the self-induced vortex energy exhibits a mean `inverse-cascade' to larger scale structures. Interestingly we observe a range of intermediate-scale structures that are preferentially sheared out during the interactions, leaving two vortex populations, one of large-scale vortices and one of small-scale vortices. We take a subset of the parameter space used for the QG study and perform simulations using a non-hydrostatic model. This system, free of the layer-wise two-dimensional constraints and geostrophic balance of the QG model, allows for the generation of inertia-gravity waves and ageostrophic advection. The study of the interactions between two co-rotating, non-hydrostatic vortices is performed over four different Rossby numbers, two positive and two negative, allowing for the comparison of cyclonic and anti-cyclonic interactions. It is found that a greater amount of wave-like activity is generated during the interactions in anticyclonic situations. We also see distinct qualitative differences between the interactions for cyclonic and anti-cyclonic regimes.

A cromodinâmica quântica (QCD) é a teoria fundamental que rege as interações fortes, cujas partículas elementares são os quarks e gluons. Em termos de escala de energia, a QCD é caracterizada pela liberdade assintótica (quarks e glúons aproximadamente livres) e confinamento de cor (quarks e gluons confinados dentro de hádrons), sendo o primeiro tratado de maneira perturbativa e o último sendo um fenômeno intrinsicamente não-perturbativo. À temperatura finita, conforme se aumenta a temperatura, a matéria hadrônica sofre uma transição de fase do tipo crossover indo de um gás de hádrons ao plasma de quarks e glúons (QGP). Na vizinhança do crossover, onde os hádrons estão ``derretendo\'\' para formar o QGP, a QCD se encontra em uma região não perturbativa e portanto o QGP nessa região é fortemente acoplado, dificultando estudos analíticos. A chamada dualidade AdS/CFT, também conhecida como holografia, aparece para oferecer uma oportunidade única para o estudo do QGP ao prover um mapa entre teorias fortemente acopladas (muito difícil de serem resolvidas) e uma teoria de gravitação clássica. Na frente experimental, o estudo do QGP é feito em aceleradores de partículas colidindo íons pesados ultrarelativísticos. Nestes experimentos, o QGP criado sofre rápida expansão, com uma intrincada interação entre escalas duras e moles de energia, do estado inicial ao estado final. Tal cenário evidencia a necessidade de formular uma teoria para o QGP que inclua propriedades fora do equilíbrio. Afortunadamente, a dualidade holográfica encaixa-se bem para essa tarefa. Resolvendo-se as equações de Einstein dependentes do tempo, um problema da área da relatividade geral numérica, é possível estudar fenômenos fora do equilíbrio de plasmas fortemente acoplados. Ademais, o diagrama de fase da QCD no plano (T,mu_B), onde T é a temperatura e mu_B o potencial químico bariônico, permanece amplamente desconhecido devido a sua natureza não-perturbativa. Em particular, é conjecturada a existência de um ponto crítico delimitando o crossover de uma transição de fase de primeira ordem. Motivados por tais fatos, esta tese utiliza a dualidade holográfica para analisar o papel do ponto crítico na dinâmica fora do equilíbrio. Por exemplo, é apresentado aqui um estudo de como o ponto crítico afeta o tempo que leva para um plasma não-Abeliano fortemente acoplado adquirir comportamento hidrodinâmico partindo de um estado completamente fora do equilíbrio. / Quantum Chromodynamics (QCD) is the fundamental theory that governs the strong interaction, whose fundamental particles are quarks and gluons. In terms of energy scales, QCD is characterized by asymptotic freedom (approximately free quarks and gluons) and color confinement (quarks and gluons confined inside hadrons), where the former can be treated perturbatively and the latter is an intrinsic non-perturbative phenomenon. At finite temperature, hadronic matter undergoes a crossover phase transition from a gas of hadrons to the quark-gluon plasma (QGP) as the temperature increases. Near the crossover, where hadrons ``melt\'\' to release quarks and gluons, QCD is in its non-perturbative regime and the QGP is strongly coupled, posing great challenges for analytical studies. The so-called AdS/CFT duality, also known as holography, comes to offer a unique opportunity to study the QGP by providing a map between strongly coupled theories (which are generally very hard to solve) and a classical theory of gravity. On the experimental front, the study of the QGP is carried out in particle accelerators by colliding ultrarelativistic heavy ions. In these experiments, the QGP created undergoes rapid expansion and there is a very intricate interplay between soft and hard scales, from initial conditions to final the stream of particles. This scenario makes it evident that one must understand the QGP also out of equilibrium. Fortunately, holography is well suited for this task. By solving the time dependent Einstein\'s equations, using general techniques previously employed in numerical general relativity, one can study non-equilibrium phenomena of strongly coupled plasmas. Furthermore, the QCD phase diagram on the (T,mu_B) plane, where T is the temperature and mu_B the baryon chemical potential, remains largely unknown due to its non-perturbative aspects. In particular, it is conjectured the existence of a critical point delimiting the crossover region from the first order phase transition. Motivated by these facts, this thesis employs holography to analyze the role of the critical point on far-from-equilibrium dynamics. For instance, it is investigated how the critical point affects the time that it takes for a strongly coupled plasma to display hydrodynamic behavior starting from a far-from-equilibrium initial state.

O objetivo desse trabalho é estudar aplicações da correspondência AdS/CFT na descrição de plasmas fortemente acoplados similares ao plasma de quarks e glúons (PQG) produzido em colisões de íons pesados no RHIC e no LHC. O projeto está articulado em duas partes. Inicialmente estudamos como alguns observáveis, como a taxa de produção de fótons e diléptons, são afetados por anisotropias espaciais presentes no plasma. Isso é importante porque o PQG produzido em experimentos do mundo real tipicamente começa em configurações de alta anisotropia, que depois evoluem para configurações isotrópicas. Para modelar a anisotropia a acoplamento forte fizemos uso de uma solução de buraco negro de supergravidade do tipo IIB encontrada recentemente em arXiv:1105.3472/hep-th. Como segunda direção de pesquisa e novamente focando em aplicações da correspondência AdS/CFT na descrição do PQG, investigamos teorias de gravidade de Lovelock, que são generalizações naturais da teoria de relatividade geral de Einstein. Essas teorias contém termos com derivadas de ordem superior ao mesmo tempo que mantém equações do movimento de segunda ordem, e por isso constituem uma arena ideal para começar a entender como termos de derivada de ordem superior afetam vários observáveis físicos do plasma. / The aim of this work is to study applications of the AdS/CFT correspondence to strongly coupled plasmas similar to the quark-gluon plasma (QGP) produced in heavy ion collisions at RHIC and LHC. The project is articulated in two parts. Initially, we will study how some observables, such as photon and dilepton production rates, are affected by spatial anisotropies present in the plasma. This is important, since the QGP produced in real world experiments generically starts in highly anisotropic configurations, which later evolve towards isotropy. To model anisotropy at strong coupling we will make use of an anisotropic black hole solution of type IIB supergravity which has been recently obtained in arXiv:1105.3472/ hep-th. As a second direction of research and again focusing on applications of the AdS/CFT correspondence to the QGP, we will investigate Lovelock theories of gravity, which are natural generalizations of Einsteins general relativity. These theories contain higher derivative terms, while maintaining the equations of motion of second order, and constitute an ideal arena where to start understanding how higher derivative corrections affect various physical observables of the plasma.

A correspondência AdS/CFT é uma notável ferramenta no estudo de teorias de gauge fortemente acopladas que podem ser mapeadas em uma descrição gravitacional dual fracamente acoplada. A correspondência é melhor entendida no limite em que ambos $N$ e $\\lambda$, o rank do grupo de gauge e o acoplamento de \'t Hooft da teoria de gauge, respectivamente, são infinitos. Levar em consideração interações com termos de curvatura de ordem superior nos permite considerar correções de $\\lambda$ finito. Por exemplo, a primeira correção de acoplamento finito para supergravidade tipo IIB surge como um termo de curvatura com forma esquemática $\\alpha\'^3 R^4$. Neste trabalho investigamos correções de curvatura no contexto da gravidade de Lovelock, que é um cenário simples para investigar tais correções pois as suas equações de movimento ainda são de segunda ordem em derivadas. Esse cenário também é particularmente interessante do ponto de vista da correspondência AdS/CFT devido a sua grande classe de soluções de buracos negros assintoticamente AdS. Consideramos um sistema de gravidade AdS-axion-dilaton em cinco dimensões com um termo de Gauss-Bonnet e encontramos uma solução das equações de movimento, o que corresponde a uma black brane exibindo uma anisotropia espacial, onde a fonte da anisotropia é um campo escalar linear em uma das coordenadas espaciais. Estudamos suas propriedades termodinâmicas e realizamos a renormalização holográfica usando o método de Hamilton-Jacobi. Finalmente, usamos a solução obtida como dual gravitacional de um plasma anisotrópico fortemente acoplado com duas cargas centrais independentes, $a eq c$. Calculamos vários observáveis relevantes para o estudo do plasma, a saber, a viscosidade de cisalhamento sobre densidade de entropia, a força de arrasto, o parâmetro de jet quenching, o potencial entre um par quark-antiquark e a taxa de produção de fótons. / The AdS/CFT correspondence is a remarkable tool in the study of strongly coupled gauge theories which can be mapped to a dual, weakly coupled gravitational description. The correspondence is best understood in the limit in which both $N$ and $\\lambda$, the rank of the gauge group and the \'t Hooft coupling of the gauge theory, respectively, are infinite. Accounting for higher curvature interactions allows one to begin to consider finite $\\lambda$. For example, the leading finite coupling corrections to type IIB supergravity arise as stringy corrections with schematic form $\\alpha\'^3 R^4$. In this work we investigate higher curvature corrections in a simpler scenario, the Lovelock gravity. Lovelock gravity is a nice framework to investigate such corrections since its equations of motion are still second order in derivatives and is particularly interesting from the point of view of the AdS/CFT correspondence because a large class of asymptotically AdS black holes solutions are known. We consider five-dimensional AdS-axion-dilaton gravity with a Gauss-Bonnet term and find a solution of the equations of motion which corresponds to a black brane exhibiting a spatial anisotropy, with the source of the anisotropy being an axion field linear in one of the spatial coordinates. We study its thermodynamics and we carry out the holographic renormalization using the Hamilton-Jacobi approach. Finally, we use the solution as a gravity dual to a strongly coupled anisotropic plasma with two independent central charges, $a eq c$. We compute several observables relevant to the study of the plasma, namely, the shear viscosity over entropy density ratio, the drag force, the jet quenching parameter, the quarkonium potential and the thermal photon production.

We study three types of theories, using supersymmetry and ideas from string theory as tools to gain understanding of systems of more general interest. Firstly, we introduce non-relativistic Chern-Simons-matter field theories in three dimensions and study their anyonic spectrum in a conformal phase. These theories have supersymmetric completions, which in the non-relativistic case suffices to protect certain would-be BPS quantities from corrections. This allows us to compute one-loop exact anomalous dimensions of various bound states of non-Abelian anyons, analyse some interesting unitarity bound violations, and test some recently proposed bosonization dualities. Secondly, we turn on a chemical potential and break conformal invariance, putting the theory into the regime of the Fractional Quantum Hall Effect (FQHE). This is illustrated in detail: the theory supports would-be BPS vortices which model the electrons of the FQHE, and they form bag-like states with the appropriate filling fractions, Hall conductivities, and anyonic excitations. This formalism makes possible some novel explicit computations: an analytic calculation of the anyonic phases experienced by Abelian quasiholes; analytic relationships to the boundary Wess-Zumino-Witten model; and derivations of a wide class of QHE wavefunctions from a bulk field theory. We also further test the three-dimensional bosonization dualities in this new setting. Along the way, we accumulate new descriptions of the QHE. Finally, we turn away from flat space and investigate a problem in (3+1)-dimensional quantum gravity. We find that even as an effective theory, the theory has enough structure to suggest the inclusion of certain gravitational instantons in the path integral. An explicit computation in a minimally supersymmetric case illustrates the principles at work, and highlights the role of a hitherto unidentified scale in quantum gravity. It also is an interesting result in itself: a non-perturbative quantum instability of a flat supersymmetric Kaluza-Klein compactification.

Three-dimensional gravity analysis is the process of removing the predictable components from the free-air gravity anomalies and has proven to be useful for interpreting the subsurface structures and active processes at mid-ocean ridges. The three-dimensional effects of the seafloor and Moho topography, assuming a constant crustal thickness and constant crust and upper mantle densities, are subtracted from the free-air anomalies, yielding the mantle Bouguer anomalies. Mantle Bouguer anomalies at mid-ocean ridges are believed to be largely due to the three-dimensional thermal structure, which can be predicted using a simple passive flow model. When the gravity contribution from the predicted thermal structure is removed from the mantle Bouguer anomalies, the residual mantle Bouguer anomalies are created, which represent lateral variations in the crustal thickness and/or density variations from the assumed model. Three-dimensional gravity analysis has been carried out over three areas along the Pacific-Antarctic East Pacific Rise (EPR): (1) the eastern intersection of the Menard transform with the EPR, (2) the overlapping spreading center (OSC) at 36.5°S and, (3) the western intersection of the Raitt transform with the EPR. This geophysical analysis provides an essential tool for understanding the subsurface crustal/upper mantle structure of the fast spreading EPR, and more specifically at transform and nontransform offsets along the EPR. Several interesting features were observed at the eastern intersection between the Menard transform and the EPR. The continuous nature of the residual mantle Bouguer anomalies along the ridge axis suggests that the 60 km of ridge axis surveyed here has a fairly uniform crustal/upper mantle structure. Significant features are not observed in the residual mantle Bouguer anomalies at the ridge-transform intersection or along the eastern 75 km of the Menard transform. At the ridge-transform intersection, fresh lavas from the observed overshot ridge have filled in the transform valley and have subsequently thickened the crust, eliminating any crustal thinning that is occurring there. The large OSC at 36.5°S has a left-stepping offset of approximately 34 km. The most significant feature in the gravity data from this study area is the observed low in the mantle Bouguer anomalies which extends from the northern ridge segment, eastward to the "inactive" rift and continued along the southern ridge segment. This gravity low suggests that this region is underlain by thicker crust and/or hotter, less dense material. No significant features are observed in the residual mantle Bouguer anomalies associated with the overlap basin or the two smaller basins that border the "inactive" rift. The western ridge-transform intersection (RTI) between the Raitt transform and the EPR significantly differs from the Menard transform study area. A transform valley is not observed at this RYE and neither is an overshot ridge. Instead, a transformparallel median ridge is observed east of the RTI, and a fossil transform valley is observed north of the RTI. A low in the residual mantle Bouguer anomalies is associated with the fossil transform valley and the median ridge, suggesting that these areas are underlain by thicker crust and/or less dense material. Positive residual mantle Bouguer anomalies observed at the inside corner of the RYE suggest that this area is underlain by thinner crust and/or colder, more dense material; while at the outside corner of the ridge-transform intersection, a residual anomaly low is observed which suggests that the outside corner is underlain with thicker crust and/or hotter, less dense material. / Graduation date: 1995 / Figures in original document are black and white photocopies. Best scan available.

Sverige är ett exportland med lång tradition av handel med omvärlden. För att kunna utnyttja våra absoluta och komparativa fördelar gäller det att vi har god kunskap om vad som påverkar vår handel. Dagens konsumenter har ett stort antal produkter att välja mellan. Handla har aldrig varit lättare och med hjälp av internet är det möjligt att handla varor från andra sidan jordklotet med minimal ansträngning. Vi ställer oss frågan, har vår språkkunskap och kultur en inverkan på den internationella handeln? Denna fråga ska försöka besvaras med hjälp av ett bland de vanligaste verktygen vid skattning av bilateral handel, den så kallade gravitationsmodellen. Gravitationsmodellen är ett bra verktyg då man med små medel kan få en hög förklaringsgrad av handeln. Eftersom kultur innehåller fler dimensioner än språk, som bland annat historia, religion, politik och värderingar, förväntades kultur ha en större inverkan på handeln. Resultatet visar att språk och kultur har en kraftig effekt på handeln och samtliga variabler visade sig vara starkt signifikanta.