Dissertations / Theses on the topic 'Space-times'
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1
Melas, Evangelos. "Aspects of asymptotically flat space-times." Thesis, Queen Mary, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398020.
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Ambrus, Victor E. "Dirac fermions on rotating space-times." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7527/.
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Quantum states of Dirac fermions at zero or finite temperature are investigated using the point-splitting method in Minkowski and anti-de Sitter space-times undergoing rotation about a fixed axis. In the Minkowski case, analytic expressions presented for the thermal expectation values (t.e.v.s) of the fermion condensate, parity violating neutrino current and stress-energy tensor show that thermal states diverge as the speed of light surface (SOL) is approached. The divergence is cured by enclosing the rotating system inside a cylinder located on or inside the SOL, on which spectral and MIT bag boundary conditions are considered. For anti-de Sitter space-time, renormalised vacuum expectation values are calculated using the Hadamard and Schwinger-de Witt methods. An analytic expression for the bi-spinor of parallel transport is presented, with which some analytic expressions for the t.e.v.s of the fermion condensate and stress-energy tensor are obtained. Rotating states are investigated and it is found that for small angular velocities Ω of the rotation, there is no SOL and the thermal states are regular everywhere on the space-time. However, if Ω is larger than the inverse radius of curvature of adS, an SOL forms and t.e.v.s diverge as inverse powers of the distance to it.
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Björnsson, Jonas. "Strings, Branes and Non-trivial Space-times." Doctoral thesis, Karlstad University, Faculty of Technology and Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1619.
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This thesis deals with different aspects of string and /p/-brane theories. One of the motivations for string theory is to unify the forces in nature and produce a quantum theory of gravity. /p/-branes and related objects arise in string theory and are related to a non-perturbative definition of the theory. The results of this thesis might help in understanding string theory better. The first part of the thesis introduces and discusses relevant topics for the second part of the thesis which consists of five papers.
In the three first papers we develop and treat a perturbative approach to relativistic /p/-branes around stretched geometries. The unperturbed theory is described by a string- or particle-like theory. The theory is solved, within perturbation theory, by constructing successive canonical transformations which map the theory to the unperturbed one order by order. The result is used to define a quantum theory which requires for consistency d = 25 + p dimensions for the bosonic /p/-branes and d = 11 for the supermembrane. This is one of the first quantum results for extended objects beyond string theory and is a confirmation of the expectation of an eleven-dimensional quantum membrane.
The two last papers deal with a gauged WZNW-approach to strings moving on non-trivial space-times. The groups used in the formulation of these models are connected to Hermitian symmetric spaces of non-compact type. We have found that the GKO-construction does not yield a unitary spectrum. We will show that there exists, however, a different approach, the BRST approach, which gives unitarity under certain conditions. This is the first example of a difference between the GKO- and BRST construction. This is one of the first proofs of unitarity of a string theory in a non-trivial non-compact space-time. Furthermore, new critical string theories in dimensions less then 26 or 10 is found for the bosonic and supersymmetric string, respectively.
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Shabbir, Ghulam. "Curvature and projective symmetries in space-times." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364690.
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In this thesis a number of problems concerning proper curvature collineations, proper Weyl collineations and projective vector fields will be considered. The work on the above areas can be summarised as: (i) A study of proper curvature collineations in plane symmetric static, spherically symmetric static and Bianchi type I spacetimes will be presented by considering the rank of their 6 x 6 Riemann tensors and using a theorem which eliminates those space-times where proper curvature collineations can not exist; (ii) A study of proper Weyl collineations is given by using the algebraic classification and associated rank of the Weyl tensor and using a theorem similar to that used in (i); (iii) A technique is developed to study projective vector fields in the Friedmann Robertson-Walker models and plane symmetric static spacetimes; (iv) The situations when conformally flat spacetimes admit proper curvature collineations are fully explored.
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Del, Bonifro Francesca. "Geodesics motion in fuzzy black hole space-times." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13512/.
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Classical General Relativity predicts the existence of space-times with non-trivial casual structures known as Black Holes. A classical black hole could form by the gravitational collapse of a compact object, which should end into a singularity covered by a (sharply defined) horizon, with a size equal to the gravitational radius of the matter source. In a quantum theory, the matter source is described by a quantum state, and one can correspondingly describe its gravitational radius by means of a Horizon Wave-Function. The resulting space-time is therefore expected to be "fuzzy", and so will be the geodesic motion of test particles. Orbits of massive particles as well as trajectories of light rays around such fuzzy gravitational sources are here analysed in details using both analytical approximations and numerical calculations. The uncertainty in the time of radial free fall and the effects on the out-going radiation emitted by the collapsing matter will also be presented.
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Mena, Filipe Artur Pacheco Neves Carteado. "Inhomogeneous and anisotropic space times in general relativity." Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252193.
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Wilson, Jonathan Peter. "Regularity of axisymmetric space-times in general relativity." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243657.
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Hobe, Stephan. "Space law: necessary changes in times of globalisation." Thesis, National Aviation University, 2021. https://er.nau.edu.ua/handle/NAU/48791.
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In 2020, we have celebrated the 60th year of space law making. Around 1959/1960 the work of the United Nations Committee on the Peaceful Uses of Outer Space and in particular its Legal Subcommittee started with a view to implement international space law. As we will show in this lecture there were different phases of space law making that all had their distinct feature.Characteristic for the first period of space law making was, on the one hand, that there was always a military overtone to the use of outer space that played a preeminent role.
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Millner, Anthony. "Noncommutative phenomena in flat and curved space-times." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/4910.
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Includes bibliographical references (leaves 88-92).This thesis aims to explore several facets of noncommutative geometry which arise in physics. In particular, our focus will be on string-inspired noncommutativity, and we will at all times try to justify the noncommutative models we study from a stringy perspective.
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Khan, Muhsan A. "Holonomy and projective symmetry in general relativity." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369628.
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A study of the holonomy group of space-time is undertaken and related to the Segre and Petrov types of then Weyl and E-tensors respectively. Attention is then focused on the E-tensor, and a theorem is proved which states that any space-time M can be disjointly decomposed into open sets on which the Segre type of the E-tensor is constant, the union of which if dense in M. This theorem is then applied to prove a similar theorem for the Ricci tensor using the principal null directions of the E-tensor. Finally, a study of proper projective symmetry in null and non-null Einstein-Maxwell and static, spherically symmetric space-times is performed. A theorem is proved which states that no proper projective symmetry is possible in any null Einstein-Maxwell space-times. This result is then extended to the non-null case under some general restrictions. The static, spherically symmetric space-times are then considered, and those admitting proper projective symmetry are completely determined. The proper projective vector fields are also explicitly calculated.
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Cundy, Mark A. "The Rarita-Schwinger equation in algebraically special space-times." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365285.
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Manuel, Kwok Keung Kevin. "Redevelopment and urban space and form : Times Square Precinct /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B14804189.
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Cremonini, Carlo Alberto. "Spin coupling to curved space-times: Melvin and double Kasner cosmologies." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14227/.
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La teoria dei campi quantistici rappresenta l'approccio moderno per descrivere tre interazioni fondamentali: la forte, la debole e l'elettromagnetica. Non è possibile descrivere la gravità come teoria di campo quantistico per via della sua non-rinormalizzabilità. La teoria dei campi quantistici su spazi-tempi curvi rappresenta un approccio moderno per descrivere le interazioni tra particelle quantistiche e campi gravitazionali. L'obiettivo di questo elaborato è di illustrare un metodo matematico completamente generale per descrivere particelle con spin in campi gravitazionali arbitrari, concentrando l'attenzione sulle implicazioni fisiche che riguardano l'interazione tra spin e campi gravitazionali. Questo apparato viene poi applicato a specifiche cosmologie, la cosmologia di Melvin e la cosmologia double Kasner. I risultati ottenuti vengono analizzati da un punto di vista fisico mostrando gli effetti che emergono dall'accoppiamento tra spin e gravità.
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Asano, Yuhma. "Emergence of Space-Times from Gauge Theories in Gauge/Gravity Duality." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199095.
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Kladouchou, Argyri. "Hidden symmetries in general relativity : killing tensors and ansiotropic space-times." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38070.
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Sasse, Fernando Deeke. "Huygens' principle for relativistic wave equations on Petrov type III space-times." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22232.pdf.
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Dang, Nguyen Viet. "Renormalization of quantum field theory on curved space-times, a causal approach." Paris 7, 2013. http://www.theses.fr/2013PA077188.
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Le sujet de la thèse est la construction d'une théorie perturbative des champs quantiques en interaction sur un espace-temps courbe, suivant un point de vue conçu par Stueckelberg et Bogoliubov et developpé par Epstein-Glaser sur l'espace de Minkowski plat. En 2000 un progrès important fut réalisé par Brunetti et Fredenhagen qui réussirent à étendre la théorie d'Epstein-Glaser en exploitant le point de vue développé par Radzikowski pour definir les états quantiques sur un espace-temps courbe en terme d'ensembles de front d'onde. Ces résultats furent ultérieurement généralisés par Fredenhagen, Brunetti, Hollands, Wald, Rejzner, etc. Aux théories de Yang-Mills et de la gravitation. Cependant, même pour des théories sans invariance de jauge, de nombreux détails mathématiques sont restés inexplorés et parfois sans vérification. Dans cette thèse, on construit d'une façon totalement rigoureuse cette théorie dans le cas des champs sans invariance de jauge. Dans mon travail, j' ai revisité complètement cette théorie, résolvant au passage plusieurs questions laissées en suspens, incorporant de nombreux résultats nouveaux autour de ce programme et, le cas échéant, apportant des détails beaucoup plus précis sur les contre-termes dans le processus de renormalisation, une compréhension plus approfondie des ambiguïtés et une description géométrique des ensembles de front d'onde. L'ensemble de la thèse utilise un large éventail de techniques mathématiques : de la géométrie différentielle et pseudo riemannienne, des techniques d'analyse micro-locale et de géométrie symplectique pour les fronts d'onde, de l'analyse fonctionnelle, des résultats fins de la théorie des distributionsThe subject of the thesis is the construction of a perturbative quantum theory of interacting fields on a curved space-time, following a point of view pioneered by Stueckelberg and Bogoliubov and developed by Epstein-Glaser on the flat Minkowski space-time. In 2000 a breakthrough was done by Brunetti and Fredenhagen who were able to extend the Epstein-Glaser theory by exploiting the point of view developed by Radzikowski to define quantum states on a curved space-time in terms of wave-front sets. These results were further extended by Fredenhagen, Brunetti, Hollands, Wald, Rejzner, etc. To Yang-Mills fields and the gravitation. However, even for theories without gauge invariance, many mathematical details were left unexplored and unquestioned. The task of Viet was precisely to derive fully rigorously this theory in the case there is no gauge invariance. In my work, I propose a complete review of the result, solving numerous questions, adding many new results around this program and, eventually, giving more precise details on the counterterms and ambiguities in the renormalization process, and a deeper understanding of the geometry of the wave front set of the n-point functions. All this thesis uses various mathematical techniques: differential and pseudo Riemannian geometry, microlocal analysis and the symplectic geometry of wavefront sets, functional analysis, fine results from the theory of distributions, Hopf algebras, etc
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Jaireth, Subhash, and Subhash Jaireth@ga gov au. "Theatre of the times of Socrates, Lunin and Nero : Time and space in Edvard Radzinskiis trilogy Theatre of the Times ." The Australian National University. Faculty of Arts, 1996. http://thesis.anu.edu.au./public/adt-ANU20091027.093131.
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Between 1969 and 1980 Edvard Radzinskii wrote three historico-political plays which were later published as a trilogy entitled Theatre of the Times
. This thesis attempts to unravel the nature of time in the trilogy and invokes Mikhail Bakhtins notion about the forms of time and the chronotope in literary narratives to do that. Bakhtinian concept of the chronotope provides a suitable strategy for reading a trilogy that aims to re-present real time, place and human beings. The concept also provides a vantage point from where the trilogy can be read both from within the time-space of its main protagonists and from that of its author, readers, performers and spectators.
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Both Dialogues with Socrates' and 'Lunin
are structured around the chronotope of the prison which is associated with the chronotope of the acropolis in Dialogues with Socrates and with the chronotope of the masked-ball in Lunin
. In Theatre of the Times of Nero and Seneca the circus-theatre functions as the main chronotope. All these chronotopes serve as plot-constitutive devices and provide appropriate space in which the lives and times of the main protagonists can be adequately re-presented. However, the use of the concept of the chronotope in reading the trilogy does not imply that it can be read meaningfully only from within the time-space of its protagonists. The trilogy reconstructs the historical time-space but also engages in a substantial way with contemporary Soviet reality. This is achieved through an interaction between literary and real chronotopes. There is little doubt that most Soviet readers, performers and spectators negotiatied the chronotopes of the prison and the circus-theatre and the motifs of show-trial and execution from within their own time-space, their own historical experience. The thesis discusses a large number of reviews published in Soviet media to show that most critics read the trilogy from within the discourses about positive hero and socialist realism, because of which Socrates and Lunin were also turned into positive heroes.
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One of the most intriguing aspect of the three plays is the play within a play structure which achieves its maximum potential in the final play of the trilogy where it is combined with the theme of metamorphoses and multiple role playing. The trilogy, like Pirandellos trilogy about theatre, is able to foreground its own theatricality and explore the role of theatricality and role playing in and outside theatre. In Theatre of the Times of Nero and Seneca the boundary between role playing in life and in theatre becomes so blurred that history begins to resemble the writing and staging of a play.
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Apart from exploring the nature of theatricality, the trilogy also questions the conventions of its genre. The three plays do not follow the conventional framing devices employed by dramatic texts and foreground the presence of a mediating narrator. This novelisation, is more evident in Lunin
in which the frequent use of verbs in the past tense in the extra-dialogic text can be linked to the presence of a mediating narrator.
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Khan, Farzad Rafi. "Beyond child labour in Pakistan's soccer ball industry : hard times in imperial space." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85175.
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Developing countries and the poor within them (i.e., the other) receive scant attention in management and organization studies (MOS). The field, thus, suffers from both ethnocentric and class biases. This research effort seeks to reduce these biases, particularly in the conversation on power taking place between MOS' critical management studies and interorganizational collaboration research streams.Articulating a case study of the Sialkot soccer ball child labour project in Pakistan (1995-2003), the thesis explores the communication constraints that are faced by weak actors in interorganizational domains (a social problem and a set of organizations having a stake or interest in that problem) located in the developing world. Relying on both written documents (private and public) and field interviews, especially with women soccer ball stitchers at the village level, a typology of communication constraints is developed. These constraints are examined from the perspectives of those at the bottom of the international supply chain and the injuries these groups suffer from them are documented in the thesis. It is found that the ability of weak actors to use communication to influence a domain is highly contingent on how space and time are configured in a domain. Domains have temporal rhythms and spatial configurations. The thesis identifies two types of temporal rhythms (technocratic and subsistence clocks) and a spatial configuration (imperial space) that severely militate against weak actors exercising agency in a domain through communication. Strategies (e.g., emergent collective struggle) that can prevent weak actors from becoming subalternalized (voiceless) in a domain are also discussed. The case study permits an investigation of contemporary transnational activism that often sires interorganizational collaboration projects in developing countries. The thesis identifies two types of transnational activism (thick and thin), delineates the various elements constituting them, and shows how thin activism can lead to interorganizational projects hurting weak and powerless groups that are intended to be assisted.
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Rinkart, Yvonne Kristin. "The production of airport space : the times, spaces and bodies of international aviation." Thesis, Aberystwyth University, 2017. http://hdl.handle.net/2160/f3347320-0c2d-490e-aa9c-2b53163d1442.
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This thesis investigates the production of airport space, and it puts a particular emphasis on its temporal, spatial and embodied characteristics. The first chapter is concerned with the work of architects and their production of representations of airport space. Building on in-depth interviews with architects, the chapter considers their use of drawings and computer models as well as their thinking about the sites where airports are located. The second chapter investigates the work of operational readiness experts, who design and test the spatial practices of the operations of new airport buildings. Making use of interviews with two operational readiness experts and my observations during terminal trials, the chapter is concerned with t he design of the trial process as well as the creation of individual trials. I investigate the scripting of volunteers to get at the understanding of the passenger as a user of airport space. The third chapter discusses the labour of cleaners and baggage handlers in maintaining airport space and enabling passengers’ movement. I interviewed union representatives, a ground handling expert and a health and safety expert to provide multiple perspectives on workers’ labour, as well as the physical consequences of their work. The fourth chapter is concerned with the impact of aircraft noise on neighbourhoods close to, and increasingly also at a distance from, airports. Building on interviews with activists and representatives of the Port Authority of New York and New Jersey, I investigate how aircraft noise is measured and represented and how its geographies are perceived, navigated, and protested by inhabitants. Throughout, the thesis aims to create an understanding of the relations between the spatial and temporal characteristics of airport space, and their impacts on the multiple subjects of airport space.
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Bengtsson, Martin. "Analytical Expressions for the Hawking Mass in slowly rotating Kerr and Kerr-Newman Space-times." Thesis, Linköping University, Department of Mathematics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9246.
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Penrose's inequality which relates the total mass of a space-time containing a black hole with the area of the event horizon, is a yet unproven condition that is required for the cosmic censorship hypothesis. It is believed that the inequality could be proved by using properties of the Hawking mass. This thesis gives analytical expressions for the Hawking mass in slowly rotating Kerr and Kerr-Newman space-times. It is also shown that the expressions are monotonically increasing, a result that does not contradict Penrose's inequality.
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Bauer, Florian [Verfasser], Manfred [Akademischer Betreuer] Lindner, and Wolfgang [Akademischer Betreuer] Hillebrandt. "The Cosmological Constant and Discrete Space-Times / Florian Bauer. Gutachter: Wolfgang Hillebrandt. Betreuer: Manfred Lindner." München : Universitätsbibliothek der TU München, 2006. http://d-nb.info/1054824037/34.
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Dawson, Simon P. "Bounds on negative energy densities in quanum field theories on flat and curved space-times." Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437627.
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Klyukovski, Andrew A. "The space race as the American dream : fantasy theme analysis of the New York Times' coverage /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060115.
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Howarth, Laura. "The existence and structure of constants of geodesic motion admitted by spherically symmetric static space-times." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310318.
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Fama, Christopher J., and -. "Non-smooth differential geometry of pseudo-Riemannian manifolds: Boundary and geodesic structure of gravitational wave space-times in mathematical relativity." The Australian National University. School of Mathematical Sciences, 1998. http://thesis.anu.edu.au./public/adt-ANU20010907.161849.
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[No abstract supplied with this thesis - The first page (of three) of the Introduction follows]
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This thesis is largely concerned with the changing representations of 'boundary' or 'ideal' points of a
pseudo-Riemannian manifold -- and our primary interest is in the space-times of general relativity. In particular, we are interested in the following question: What assumptions about the 'nature' of 'portions' of a certain 'ideal boundary' construction (essentially the 'abstract boundary' of Scott and Szekeres (1994)) allow us to define precisely the topological type of these 'portions', i.e., to show that different representations of this ideal boundary, corresponding to different embeddings of the manifold into others, have corresponding 'portions' that are homeomorphic?
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Certain topological properties of these 'portions' are preserved, even allowing for quite unpleasant properties of the metric (Fama and Scott 1995). These results are given in Appendix D, since they are not used elsewhere and, as well as representing the main portion of work undertaken under the supervision of Scott, which deserves recognition, may serve as an interesting example of the relative ease with which certain simple results about the abstract boundary can be obtained.
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An answer to a more precisely formulated version of this question appears very diffcult in general. However, we can give a rather complete answer in certain cases, where we dictate certain 'generalised regularity' requirements for our embeddings, but make no demands on the precise functional form of our metrics apart from these. For example, we get a complete answer to our question for abstract boundary sets which do not 'wiggle about' too much -- i.e., they satisfy a certain Lipschitz condition -- and through which the metric can be extended in a manner which is not required to be differentiable (C[superscript1]), but is continuous and non--degenerate. We allow similar freedoms on the interior of the manifold, thereby bringing gravitational wave space-times within our sphere of discussion. In fact, in the course of developing these results in progressively greater generality, we get, almost 'free', certain abilities to begin looking at geodesic structure on quite general pseudo-Riemannian manifolds.
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It is possible to delineate most of this work cleanly into two major parts. Firstly, there are results which use classical geometric constructs and can be given for the original abstract boundary construction, which requires differentiability of both manifolds and metrics, and which we summarise below. The second -- and significantly longer -- part involves extensions of those constructs and results to more general metrics.
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Mota, João. "Beyond visibility and monumentality : photographic images in the public space : a study for two cases, Terreiro do Paço-Lisbon, Times Square-New York." Doctoral thesis, Universidade de Aveiro, 2001. http://hdl.handle.net/10773/15329.
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Doutoramento em DesignThis thesis seeks to address the issue of retrieving / adapting the tradition of site-specific large-scale images, (other than images commercially motivated) to contemporary architectural spaces. To achieve this we discussed a conceptual framework to introduce the constitutive and operative concepts of visual public art and spatial politics. Then we made a historical overview of former uses of images in the public arena with special emphasis in the public visual art produced after 1960. Based on those operative concepts, historical framework and on the analytical tools developed during this study, we developed a methodology for designing sitespecific large-scale images in the public space. This methodology is aimed at guiding the production of largescale visual art sensible to the different contexts playing an important role in the becoming of the project, and to incite a sense of placeness on the sites for which large-scale images were proposed. In this study we produced and discussed a group of projects for large-scale images for the squares: Terreiro do Paço – Lisbon and Times Square – New York City. Those projects were guided by the same design method and with the objective of making visible the memory and the contemporaneity of the squares in study. The choice of sites with such different cultural and historical background, was instrumental for understanding the feasibility of a method intended to help the production of large-scale images set in urban environments, sensible and related to complex contexts. The choice of these squares is based on the fact that both squares are unavoidable representations of power (governmental, financial, commercial), a condition that was instrumental in our study for making clear the implications that the history, the public sphere and the public space have on the context and on the actors that have a decisive role in the production of visual art in the public space. The images proposed for the two squares were not confined to photographic images, yet they played a central role. Beyond their instrumental value for the discussion of the method proposed, those projects were concerned with the production of informed commentaries pertinent to the squares in study. To achieve this, the proposed projects made use of their size, monumentally and visibility for the creation of places that stimulate a dwelling experience sensible to the specificity of the place. As a result some projects unveiled new paths/uses for the design of largescale images in the contemporary public space.
Esta tese pretende debater a questão de reaver a tradição do uso de imagens de grandes dimensões (outras que as imagens com motivação comercial) para os espaços arquitectónicos contemporâneos. Para alcançar estes objectivos, foi necessário entender a estrutura conceptual dos conceitos constitutivos e operativos da arte visual pública e da política do espaço. Seguidamente fizemos uma abordagem histórica dos usos de imagens no espaço público, com especial ênfase na arte pública produzida depois de 1960. Consequentemente, baseados nesses conceitos operativos, referências históricas e nos instrumentos analíticos desenvolvidos neste estudo, formulámos uma metodologia projectual para a criação de imagens de grandes dimensões no espaço público. Esta metodologia pretendeu ser um princípio orientador para a produção de arte visual de grandes dimensões, sensível aos diferentes contextos que têm um papel importante no devir do projecto, e se possível estimular um sentido de lugar nos locais para os quais as imagens de grandes dimensões foram criadas. Neste estudo, produzimos e discutimos um conjunto de projectos de imagens de grandes dimensões para as praças: Terreiro do Paço – Lisboa e Times Square – Nova Iorque. Estes projectos tiveram como princípio orientador o mesmo método projectual e foram planeados para tornar visível as questões significantes da memória e da contemporaneidade das praças em estudo. A escolha de locais com um contexto histórico tão diferente, foi instrumental para verificar a viabilidade de um método que tem a intenção de possibilitar a produção de imagens de grandes dimensões sensíveis à complexidade do contexto sobre o qual a sua existência depende. Além disso a escolha destas praças foi fundamentada no facto de ambas as praças serem inevitáveis representações do poder (governamental, financeiro, comercial). Uma condição que no nosso estudo foi instrumental para tornar claras as implicações que a história, a esfera pública e o espaço público têm no contexto e nos actores que têm um papel decisivo para o devir da arte visual nos espaços públicos. As imagens propostas para estas duas praças não foram restritas às imagens fotográficas, contudo estas tiveram um papel decisivo. Esses projectos, para além do seu valor instrumental na discussão do método proposto, visaram a produção de comentários esclarecidos sobre as praças em estudo, servindo-se da escala, monumentalidade e visibilidade inerente à natureza destes projectos, para a criação de lugares que estimulassem uma experiência de habitar sensível à especificidade do lugar. Consequentemente, alguns projectos revelaram novos rumos/usos para o design de imagens de grandes dimensões no espaço público contemporâneo.
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Vollmer, Andreas [Verfasser], Vladimir Jurʹevič [Gutachter] Matveev, Vsevolod V. [Gutachter] Shevchishin, and Boris I. [Gutachter] Kruglikov. "First integrals in stationary and axially symmetric space-times and sub-riemannian structures / Andreas Vollmer ; Gutachter: Vladimir Ju. Matveev, Vsevolod V. Shevchishin, Boris I. Kruglikov." Jena : Friedrich-Schiller-Universität Jena, 2016. http://d-nb.info/1177612852/34.
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Gu, Yan [Verfasser], Thomas [Akademischer Betreuer] Herzog, Qizhi [Gutachter] Mao, Peter [Gutachter] Latz, and Thomas [Gutachter] Herzog. "Cities within cities : An examination of urban space use and transformation in ancient and modern times / Yan Gu ; Gutachter: Qizhi Mao, Peter Latz, Thomas Herzog ; Betreuer: Thomas Herzog." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/1230061088/34.
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Almotairi, Saleh Ibrahim Bakr. "Using honeypots to analyse anomalous Internet activities." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/31833/1/Saleh_Almotairi_Thesis.pdf.
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Monitoring Internet traffic is critical in order to acquire a good understanding of threats to computer and network security and in designing efficient computer security systems. Researchers and network administrators have applied several approaches to monitoring traffic for malicious content. These techniques include monitoring network components, aggregating IDS alerts, and monitoring unused IP address spaces. Another method for monitoring and analyzing malicious traffic, which has been widely tried and accepted, is the use of honeypots. Honeypots are very valuable security resources for gathering artefacts associated with a variety of Internet attack activities. As honeypots run no production services, any contact with them is considered potentially malicious or suspicious by definition. This unique characteristic of the honeypot reduces the amount of collected traffic and makes it a more valuable source of information than other existing techniques. Currently, there is insufficient research in the honeypot data analysis field. To date, most of the work on honeypots has been devoted to the design of new honeypots or optimizing the current ones. Approaches for analyzing data collected from honeypots, especially low-interaction honeypots, are presently immature, while analysis techniques are manual and focus mainly on identifying existing attacks. This research addresses the need for developing more advanced techniques for analyzing Internet traffic data collected from low-interaction honeypots. We believe that characterizing honeypot traffic will improve the security of networks and, if the honeypot data is handled in time, give early signs of new vulnerabilities or breakouts of new automated malicious codes, such as worms. The outcomes of this research include: • Identification of repeated use of attack tools and attack processes through grouping activities that exhibit similar packet inter-arrival time distributions using the cliquing algorithm; • Application of principal component analysis to detect the structure of attackers’ activities present in low-interaction honeypots and to visualize attackers’ behaviors; • Detection of new attacks in low-interaction honeypot traffic through the use of the principal component’s residual space and the square prediction error statistic; • Real-time detection of new attacks using recursive principal component analysis; • A proof of concept implementation for honeypot traffic analysis and real time monitoring.
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Lange, Steffen. "Chaotic transport and trapping close to regular structures in 4D symplectic maps." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-208418.
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Higher-dimensional Hamiltonian systems usually exhibit a mixed phase space in which regular and chaotic motion coexist. While regular trajectories are confined to regular tori, chaotic trajectories can be transported through a web of so called resonance channels which disrupt the regular structures. The focus of this thesis are time-discrete 4D symplectic maps which represent the lowest dimensional system for which the chaotic transport can circumvent regular tori. While the dynamics of 2D maps are well established, many fundamental questions are open for maps of dimension four and higher due to this property. In particular, the mechanism of the power-law trapping is unknown for these maps. In this thesis, the organization and hierarchy of the regular structures of 4D maps is uncovered and the slow chaotic transport close to these structures is examined. Specifically, this transport is shown to be organized by a set of overlapping resonance channels. The transport across these channels is found to be governed by partial transport barriers. For the transport along a channel a stochastic process including a drift is conjectured. Based on each of these two types of chaotic transport a possible mechanism for the power-law trapping in higher-dimensional systems is proposed.
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Mendonça, Rosa Helena de. "Educação nas redes: professores em cotidianos de produções televisivas." Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7622.
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O que fazem profissionais de educação numa produção televisiva? Nesta pesquisa, por meio de 'conversas' com praticantespensantes que atuam em produção de TV, e no uso de outros documentos (programas editados, argumentos, textos e roteiros), busco responder a essa pergunta e compreender as redes de conhecimentos e significações relativas aos espaçostempos de ação desses profissionais, entendidos como entre-lugares de educação e comunicação. A pesquisa, na perspectiva dos estudos com os cotidianos, se articula ao GRPESQ Currículo, redes educativas e imagens, do Laboratório Educação e Imagem/ProPEd/UERJ, e busca apoio em conversas/narrativas com/de professores que trabalharam/trabalham em televisão em especial, no programa Salto para o Futuro integrando a equipe de educação da TV Escola (MEC), ou atuando como consultores de séries temáticas. Sobre o assunto, também foram ouvidos responsáveis pela assessoria pedagógica dos canais Encuentro e Pakapaka, na Argentina, em doutorado-sanduíche, com o apoio da Capes. Como fundamentação teórica, além de pesquisas com os cotidianos, a partir de textos de Michel de Certeau, de Nilda Alves e de Inês Barbosa de Oliveira, dos quais emergem algumas das noções que permeiam essa investigação, ressalto a contribuição de autores da sociologia, como Pierre Bourdieu e Boaventura de Sousa Santos e, ainda, de represe ntantes dos chamados estudos culturais, entre eles Jesús Martín-Barbero, Nestor Canclini, Stuart Hall, Homi Bhabha entre outros. A questão do outro, da alteridade, que permeia a tese, em sua tessitura com narrativas e imagens, busca inspiração também nos escritos e em conversas com Carlos Skliar e nos textos de Jorge Larrosa. As conclusões possíveis destacam a importância das ações desses profissionais (professores) nesses espaçostempos televisivos.What do professionals in education do in a television production? This research is an attempt to answer this question not only through conversations with the practitioners engaged in television production but also through sources such as edited programmes, arguments , texts and scripts. In doing so, I intend to understand the net of knowledge and meanings related to the so called space-times of action (here understood as an in-between place belonging to both education and communication fields) of these professionals. This work, under the perspective of everyday life studies, is aligned with the research group entitled Curriculum, educational networks and images, from the Education and Image Laboratory of the post graduation program in Education (ProPEd) of the University of Rio de Janeiro State (UERJ). It concentrates in talks with and narratives of educators who worked and have been working either as members of TV Escola which belongs to the Ministry of Education (MEC) or consultants of a particular educational television program entitled Salto para o Futuro. The ones responsible for the pedagogical consultancy of the channels Encuentro and Pakapaka from Argentina have also been interviewed thanks to a doctorate program supported by Capes. The theoretical framework is based on the writings of Michel de Certeau, Nilda Alves and Ines Barbosa de Oliveira; besides them, the contributions of the sociological thinkers Pierre Bourdieu and Boaventura de Souza Santos as well as some representatives of cultural studies such as Jesús Martín Barbero, Nestor Canclini, Stuart Hall, Homi Bhabha, among others, have also been used. Issues about the other and alterity have found inspiration in Carlos Skliar and Jorge Larrosas texts. The possible conclusions made highlight the relevance of the actions of these professionals (teachers) in this space-time television environment
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Baltazar, Halyson Irene. "Métricas críticas do funcional volume e não-existência de múltiplos buracos negros em espaço-tempo estático." reponame:Repositório Institucional da UFC, 2017. http://www.repositorio.ufc.br/handle/riufc/23946.
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BALTAZAR, H. I. Métricas críticas do funcional volume e não-existência de múltiplos buracos negros em espaço-tempo estático. 2017. 67 f. Tese (Doutorado em Matemática) – Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2017.Submitted by Andrea Dantas (pgmat@mat.ufc.br) on 2017-07-12T19:24:59Z No. of bitstreams: 1 2017_tese_hibaltazar.pdf: 449308 bytes, checksum: a4275b6fceeb5cb76fe217e956f933cd (MD5)
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This work is divided in two parts. In the first one we prove a Böchner type formula for critical metrics of the volume functional on compact manifolds with fixed metric on boundary (such critical metrics are called Miao-Tam critical metrics). As an application, we derive an integral formula that will be crucial to deduce a generalization of a result obtained by Miao and Tam in 2011 for the Einstein case. More precisely, we prove that a Miao-Tam critical metric with parallel Ricci curvature must be isometric to a geodesic ball in a simply connected space form Rn, Sn or Hn. Furthermore, in dimension 3, we prove that critical metrics with non-negative sectional curvature are precisely geodesic balls of R3 or S3. Moreover, we generalize a result due to Kim and Shin (2016), replacing the harmonic Weyl tensor condition by the second order divergence free Weyl tensor condition (i.e., div2W = 0), which is weaker that the former. To be precise, we shall show that a 4-dimensional Miao-Tam critical metric, with boundary isometric to a standard sphere S3 and satisfying div2W = 0 is isometric to a geodesic ball in a simply connected space form R4, S4 or H4. At the same time, we get some rigidity results for positive static triples. In the second part, we study static vacuum space-times, which can be seen as a special case of the V-static metrics for complete Riemannian manifolds with null scalar curvature. In this case, we focus our attention on four dimensions. We prove that there are no multiple black holes on static vacuum space-times with half harmonic Weyl tensor (i.e., divW+ = 0).
Esse trabalho está dividido em duas partes. A primeira delas está relacionada ao estudo de fórmulas tipo-Böchner para métricas críticas do funcional volume em variedades compactas com métrica fixada no bordo (estas são conhecidas como métricas críticas de Miao-Tam). Como aplicação, estabeleceremos uma fórmula integral que permitirá generalizar o resultado obtido por Miao e Tam em 2011 para o caso Einstein, mais precisamente, provaremos que métricas críticas de Miao-Tam com curvatura de Ricci paralelo são isométricas às bolas geodésicas em um espaço forma simplesmente conexo Rn, Sn ou Hn. Se nos restringirmos às variedades com dimensão 3, veremos que tais estruturas se mostram ainda mais rígidas, a saber, provaremos que métricas críticas com curvatura seccional não-negativa são precisamente as bolas geodésicas de R3 ou S3. Além disso, generalizamos o resultado obtido por Kim e Shin (2016) substituindo condição de harmonicidade do tensor de Weyl pela hipótese que o tensor de Weyl tem divergente de segunda ordem nulo (i.e., div2W = 0). Mais precisamente, mostraremos que métricas críticas de Miao-Tam em dimensão 4, com bordo isométrico a esfera S3 e satisfazendo div2W = 0, são isométricas às bolas geodésicas em um espaço forma simplesmente conexo R4, S4 ou H4. Concomitantemente, obtemos resultados de rigidez para triplas estáticas positivas. Na segunda parte do trabalho, estudaremos o espaço-tempo estático no vácuo, o qual pode ser visto como um caso especial das mátricas V-estáticas para variedades completas com curvatura escalar nula. Neste caso, restringiremos nosso estudo a quarta dimensão e provaremos que não existem múltiplos buracos negros em um espaço-tempo estático no vácuo com a parte autodual do tensor de Weyl harmônico (i.e., divW+ = 0).
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Cozzella, Gabriel [UNESP]. "Information loss in black holes and the unitarity of quantum mechanics." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/143416.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A teoria quântica de campos em espaços-tempos curvos é o arcabouço teórico mais sólido que temos para estudar a interação entre gravitação e mecânica quântica na ausência de uma teoria completa de gravitação quântica. Neste contexto, um problema que atraiu muita atenção dos físicos teóricos nas últimas décadas é o chamado “paradoxo da perda de informação em buracos negros”, onde a evolução de um estado quântico puro inicial para um estado quântico misto final caracterizaria uma violação das leis da mecânica quântica. Nesta dissertação nós argumentamos que a perda de informação em si não viola as leis da mecânica quântica e é consequência direta da teoria semi-clássica utilizada. Finalmente, argumentamos que a questão da recuperação da informação deve ser tratada utilizando-se uma teoria de gravitação quântica ainda desconhecida.
The quantum theory of fields in curved space-times is the most solid framework for studying the interplay between gravity and quantum mechanics in the absence of a complete theory of quantum gravity. In this scenario, one problem that has drawn much attention from the theoretical physics community in the last decades is the so-called “black hole information loss paradox”, where the evolution from an initial pure quantum state to a final mixed quantum state would constitute a violation of the laws of quantum mechanics. In this dissertation we argue that information loss does not violate quantum mechanics, being simply a consequence of the semi-classical framework adopted and that the question of information recovery needs to be addressed by a yet unknown theory of quantum gravity.
FAPESP: 2014/08684-9
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Paixão, Oswaldo Pedreira. "Analise do balanço harmonico multi-niveis para circuitos de RF não-lineares em grande-escala via os metodos de Newton-Krylov e do tensor-Krylov." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260407.
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Orientador: Hugo Enrique Hernandez FigueroaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Este trabalho, tem como objetivo o desenvolvimento de novas técnicas, para análise de regime permanente não-autonoma de circuitos de alta-velocidade não-lineares em grande-escala. Para tal, é proposto um novo método do balanço harmônico (BH) fundamentado em uma eficiente metodologia de decomposição multi-níveis, que subdivide um circuito não-linear em grande escala em uma estrutura hierarquica de super-redes (SuRs) esparsamente interconectadas. Mais precisamente, em cada nível de hierarquia, o circuito é composto por SuRs intermediárias, SuRs de fundo, e redes de conexão (RCs). As SuRs de fundo são decompostas em um aglomerado de subredes não-lineares (SRNs) correspondendo a dispositivos semicondutores, que por sua vez, estão envolvidos por uma sub-rede linear (SRL). A equação de estado e de sonda das SuRs de fundo foram obtidas utilizando uma nova metodologia que combina a formulação de espaço de estado (FEE) para as SRNs com a formulação nodal modificada (FNM) para a SRL. Esta metodologia FEE/FNM produz um sistema quadrado de equações com menor tamanho possível. Para realização das conversões do sinal entre os domínios do tempo e da frequência, foram discutidas e implementadas diferentes transformadas de Fourier discreta (TFDs), para operação em regime multi-tons, incluindo sinais com modulação digital. A equação determinante do BH multi-níveis do circuito assume uma estrutura hierarquica do tipo bloco diagonal com borda , que pode ser eficientemente resolvida utilizando técnicas de processamento paralelo. A matriz jacobiana de cada SuR de fundo é processada utilizando eficientes técnicas de matrizes esparsas, junto com o conceito de espectro de derivada. Para a solução da equação determinante, foram utilizados os métodos de Newton e do tensor para problemas de pequena- e média-escala, e os métodos de Newton inexato e do tensor inexato para problemas em grande-escala. A globalização via pesquisa-em-linha com retrocedimento, foi adotada para nestes solucionadores não-lineares. Entretanto, para o método do tensor e do tensor inexato, também foi adotada a técnica de pesquisa-em-linha curvilinear. Nos métodos inexatos, técnicas de pré-condicionamento foram utilizadas, para aumentar a eficiência e a robustez do solucionador linear iterativo em subespaço de Krylov (GMRES, GMRES-Bt e TGMRES-Bt). Finalmente, a formulação proposta foi validada e a eficiência do método do tensor e do tensor inexato comparada com o método de Newton e de Newton inexato, para diferentes topologias de circuitos utilizando diodos, FETs e HBTs, e operando sob diferentes regimes de excitação multi-tons.
Abstract: This work deals with the development of new techniques for nonautonomous nonlinear steady-state analysis of high-speed large-scale integrated circuits. To this end, it is proposed a novel harmonic balance (HB) method fundamented on a efficient multi-level decomposition methodology, that divides a large-scale circuit into hierarchical structure of sparsely interconnected supernetworks (SuNs). More precisely, the circuit is composed by intermediary SuRs, bottom SuRs and connection networks (CNs). The bottom SuNs are decomposed into a cluster of nonlinear subnetworks (NSNs) corresponding to the opto-electronic semiconductor devices, which in turn, are embedded by a linear subnetwork (LSN). Multi-port elements can be included in the LSN, in order to use measured data or results from electromagnetic analysis of structures with complex geometries. The formulation of the bottom SuN state and probe equations uses an improved table-oriented statespace formulation (SSF), that produces a square system with the lowest possible size, which is equal to the number of nonlinear state-variables (branch voltages and currents) that act as argument of the fuctions representing the semiconductor devices nonlinearities. The SSF is compared with the classical modified nodal formulation (MNF). For dealing with signal timefrequency conversions, discrete Fourier transform (DFT) techniques for different multi-tone regimes are discussed, including complex digitally modulated signals. The multi-level HB determining equation of the circuit assumes a hierarchical block bordered structure that can be efficiently tackled by parallel processing techniques. The HB jacobian matrix is handled using efficient sparse matrix techniques with a proper definition of the derivatives spectra. For the solution of a large-size HB problem, we investigated the applications of inexact tensor method based on Krylov-subspace techniques. Preconditioning are used to improve the robustness of the iterative tensor solver. To determine the circuit DC regime, we employ the tensor method. We adopted the backtracking linesearch technique as a globalisation strategy. However, for the tensor method, in particular, a curvilinear linesearch was also implemented. Finally, the formulation was validated and, the tensor and inexact tensor method efficiency was compared with the Newton and inexact Newton method, respectively, for several different circuits using diodos, FETs and HBTs, and operating under different multi-tone regimes.
Doutorado
Engenharia de Telecomunicações
Doutor em Engenharia Elétrica
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Micheletti, Sandro Marcio Rodrigues. "Vínculos observacionais em modelos de energia escura interagente." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-30102009-143105/.
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Neste trabalho foi investigada a possibilidade de haver uma interação entre a energia e a matéria escuras. Adotamos um espaço-tempo de Friedmann-Robertson-Walker plano e dois modelos de energia escura interagente. No primeiro, o termo de interação, presente nas equações de conservação da energia e da matéria escuras, foi obtido a partir de argumentos fenomenológicos. No segundo, esse foi derivado de primeiros princípios. Ambos os modelos foram comparados com dados observacionais recentes e, em ambos os casos, obtivemos uma estimativa da constante de acoplamento diferente de zero com um desvio padrão de confiança. Além disso, em ambos os casos o sinal da constante de acoplamento é compatível com a energia escura se convertendo em matéria escura, fornecendo um alívio para o problema da coincidência.In the present work the possibility of a dark energy interacting with dark matter has been investigated. We considered a flat Friedmann-Robertson-Walker space-time with two alternative interacting dark energy models. In the first, the interaction term, appearing in the energy conservation equations was introduced by purely phenomenological reasons. In the second, it has been obtained from a given Lagrangian density. In both cases we compared the results with recent observational data and obtained an estimate of the coupling constant, which is nonvanishing by one standard deviation. Moreover, in both cases the sign of the coupling constant is compatible with dark energy decaying into dark matter, providing an alleviation to the coincidence problem.
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Cavalcante, Everton. "Aspectos geométricos da molécula de fulereno em referenciais não-inerciais." Universidade Federal da Paraíba, 2015. http://tede.biblioteca.ufpb.br:8080/handle/tede/9557.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this thesis we study the dynamics of charge carriers, and the electronic properties, of the C60 fullerene molecule. Characterizing it by a geometric bias. In inertial reference systems and when we have your material under rotation content. Initially we discussed the scientific advent of carbon allotropes, and the importance of modelling its derivates at low energies. We show that at low energies, the graphene - the two-dimensional carbon allotrope form - can be described for a non-massive theory of free fermions. At a second moment, we extended the nonmassive free fermions theory for the C60 molecule. Assuming the hexagonal graphene network can be entered in fullerene when we introduce topological defects. A brief study of topological defects in condensed matter was done. And soon after, we made a description these defects via a non-Euclidean geometry. Showing how the charge carriers in the network see the defects like gauge fields. Then we began to expose the results of this thesis. First we assume the fullerene by a two-dimensional spherical metric with defects, containing a fictitious t’Hooft-Polyakov monopole in its center. TheC60 is still subjected to the action of an Aharonov-Bohm flux arising of a magnetic wire running through its poles. So we get the spectrum, and the prediction of a persistent current in the molecule. Finally we return to the analysis of the molecule, now with your content of matter under rotation. For this, we studied a metric Gödel-type with spherical symmetry. We discussed the problem of causality and obtain the spectrum and the persistent current in terms of the vorticity (W) of spacetime.
Nesta tese estudamos a dinâmica de portadores de carga, e as propriedades eletrônicas, na molécula de fulerenoC60. Caracterizando-a por um viés geométrico. Tanto em sistemas de referência inercial, como quando temos seu conteúdo de matéria sob rotação. Inicialmente abordamos o advento científico das formas alotrópicas do carbono e a importância da modelagem a baixas energias dos seus derivados. Onde mostramos que no limite de baixas energias, o grafeno - que trata-se da forma alótropica bidimensional do carbono - pode ser descrito por uma teoria de férmions livres sem massa. Num segundo momento estendemos a teoria de férmions não massivos para a molécula de C60. Assumindo que a rede hexagonal do grafeno pode inscrever o C60 ao introduzirmos alguns defeitos topológicos. Um breve estudo sobre os defeitos topológicos na matéria condensada foi feito. Onde, logo em seguida, partimos para uma descrição de tais defeitos via uma geometria não-euclidiana. Mostrando como os portadores de carga no meio enxergam os defeitos como campos de gauge. Em seguida começamos a expor os resultados desta tese. Primeiramente assumimos tratar o fulereno por uma métrica de uma esfera bidimensional com defeitos, e contendo um monopolo de t’Hooft-Polyakov fictício em seu centro. O C60 é ainda submetido a ação de um fluxo de Aharonov-Bohm advindo de uma corda magnética quiral transpassando seus polos. Obtemos assim o espectro e a predição de uma corrente persistente na molécula. Por fim retomamos a análise da molécula, agora com seu conteúdo de matéria sob rotação. Para isso assumimos tratar o fulereno por uma métrica do tipo Gödel com simetria esférica. Discutimos o problema da causalidade e obtemos espectro e corrente persistente em termos da vorticidade (W) do espaço-tempo.
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Pereira, Dante Donizeti. "Abordagem efetiva em teorias de campos: aspectos clássicos e quânticos." Universidade Federal de Juiz de Fora (UFJF), 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/4892.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Nesta tese exploramos diferentes aspectos de teorias clássicas e quânticas de campos. Na parte clássica, examinamos o fenômeno da birrefringência eletro-magneto-óptica em ele-trodinâmica não-linear no contexto de meios materiais dielétricos não-lineares como uma correção efetiva à teoria linear maxwelliana do eletromagnetismo. Na parte quântica, seguindo o método do heat kernel em teoria quântica de campos sobre espaços curvos, derivamos e estudamos a estrutura das divergências a 1-loop para a ação efetiva de diferentes modelos. Em particular, no ramo do modelo de Yukawa, exibimos duas novas formas de ambiguidades as quais tomam lugar na ação efetiva de campos fermiônicos através do fenômeno da anomalia multiplicativa não-local. Além disso, analisamos a estrutura das divergências ultravioletas a 1-loop para um modelo recentemente proposto de gravitação massiva livre de fantasmas, e mostramos que esse modelo encontra sérias dificuldades no nível quântico.
In this thesis we explore different aspects in classical and quantum field theories. In the classical part, we examine the phenomenon of electro-magneto-optical birefringence in nonlinear electrodynamics in the context of nonlinear dielectric media as an effective correction to the linear Maxwellian theory of electromagnetism. In the quantum part, following the heat kernel method in quantum field theory on curved spaces, we derive and study the structure of the 1-loop divergences for the effective action of different models. In particular, through the Yukawa model, we show two new forms of ambiguities which take place in the effective action of fermionic fields through the phenomenon of nonlocal multiplicative anomaly. Moreover, we analyzed the structure of ultraviolet divergences at 1-loop for a recently proposed ghost-free massive gravity model, and we show that this model meets serious difficulties at the quantum level.
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Schachermayer, Walter, and Werner Schachinger. "Is there a predictable criterion for mutual singularity of two probability measures on a filtered space?" SFB Adaptive Information Systems and Modelling in Economics and Management Science, WU Vienna University of Economics and Business, 1999. http://epub.wu.ac.at/1600/1/document.pdf.
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The theme of providing predictable criteria for absolute continuity and for mutual singularity of two density processes on a filtered probability space is extensively studied, e.g., in the monograph by J. Jacod and A. N. Shiryaev [JS]. While the issue of absolute continuity is settled there in full generality, for the issue of mutual singularity one technical difficulty remained open ([JS], p210): "We do not know whether it is possible to derive a predictable criterion (necessary and sufficient condition) for "P'T..." (expression not representable in this abstract). It turns out that to this question raised in [JS] which we also chose as the title of this note, there are two answers: on the negative side we give an easy example, showing that in general the answer is no, even when we use a rather wide interpretation of the concept of "predictable criterion". The difficulty comes from the fact that the density process of a probability measure P with respect to another measure P' may suddenly jump to zero. On the positive side we can characterize the set, where P' becomes singular with respect to P - provided this does not happen in a sudden but rather in a continuous way - as the set where the Hellinger process diverges, which certainly is a "predictable criterion". This theorem extends results in the book of J. Jacod and A. N. Shiryaev [JS]. (author's abstract)Series: Working Papers SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
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Rossi, Salvemini Clara. "Espace-temps globalement hyperboliques conformément plats." Phd thesis, Université d'Avignon, 2012. http://tel.archives-ouvertes.fr/tel-00934781.
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Les espace-temps conformément plats de dimension supérieure ou égal à 3 sont des variétés localement modelées l'espace-temps d'Einstein où il agit la composante connexe de l'identité du groupe des difféomorfismes conformes.Un espace-temps M est globalement hyperbolique s'il admet une hypersurface S de type espace qui est rencontrée une et une seule fois par toute courbe causale de M. L'hypersurface S est alors dite hypersurface de Cauchy de M.L'ensemble des espace-temps globalement hyperboliques conformément plats, identifiés à difféomorphisme conforme près, est naturellement muni d'une relation d'ordre partielle: on dit que N étends M s'il existe un plongement conforme de M dans N tel que l'image de toute hypersurface de Cauchy de M est une hypersurface de Cauchy de N. Les éléments maximaux par rapport à cette relation d'ordre sont appelés espace-temps maximaux.Le premier résultat qu'on a prouvé est l'existence et unicité de l'extension maximale pour un espace-temps conformément plat globalement hyperbolique donné. Ce résultat généralise un théorème de Choquet-Bruhat et Geroch relatif aux espace-temps solutions des équation d'Einstein.L'unicité de l'extension maximale permet de prouver le résultat suivant:Théorème:En dimension supérieur ou égal à 3, l'espace d'Einstein est le seul espace-temps conformément plat maximal simplement connexe admettant une hypersurface de Cauchy compacte.Si l'hypersurface de Cauchy S du revêtement universel d'un espace-temps M est compacte on obtient donc que M est un quotient fini de l'espace d'Einstein. La structure des géodésiques de l'espace d'Einstein et l'unicité de l'extension maximale permettent de prouver :Théorème:Soit M un espace-temps conformément plat maximal de dimension supérieur ou égal à 3, qui contient deux géodésiques lumières distinctes, librement homotopes et ayant les mêmes extrémités. Alors M est un quotient fini de l'espace d'Einstein.Dans le cas où l'hypersurface S' du revêtement universel M' de M est non compacte on montre chaque point p de M' est déterminé par le compact de S 'constitué par l'intersection de son passé causal ou de son futur causal avec l'hypersurface S', suivant que p appartient au passé ou au futur de S'. Onappelle ce compact l'ombre de p sur S'. L'espace-temps M' s'identifie donc à un sous-ensemble des compacts de S'.Ce point de vue permet d'avoir une compréhension plus profonde de la maximalité d'un espace-temps. En fait on a différentes notions de maximalité :un espace-temps pourrait être maximal parmi les espace-temps conformément plats mais avoir un majorant qui n'est pas conformément plat, i.e. il pourrait exister un plongement conforme dans un espace-temps globalement hyperbolique qui ne soit pas conformément plat.Grâce à la notion d'ombre, on prouve que la structure causale induite sur la frontière de Penrose du revêtement universel d'un espace-temps conformément plat permet de caractériser les espace-temps maximaux parmi tous les espace-temps globalement hyperboliques, on obtient:Théorème:Tout espace-temps globalement hyperbolique conformément plat M qui est maximal parmi les espace-temps globalement hyperbolique conformément plats est aussi maximal parmi tous les espace-temps globalement hyperboliques.On conclut avec une discussion détaillée sur la maximalité des espaces-temps globalement hyperboliques maximaux parmi les espace-temps à courbure constante, suivant le signe de la courbure: lorsque la courbure est négative ou nulle, l'espace-temps est maximal aussi parmi tous les espace-temps globalement hyperboliques, mais cela n'est jamais vrai lorsque la courbure est strictement positive
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Lenoir, Jean-Michel. "Temps de cohérence temporelle de structures turbulentes porteuses de scalaires passifs au sein d'une turbulence homogène quasi-isotrope." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00819861.
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Le but principal du présent travail est ainsi de réaliser une expérience de mélange par la turbulence, dans laquelle il est possible de déterminer et de quantifier les temps de cohérence des différentes échelles spatiales des fluctuations du champ de vitesse et du champ de concentration qu'il transporte et mélange. La turbulence est ici voisine de la situation idéale statistiquement homogène et isotrope, et la configuration est conçue pour qu'il en soit de même pour le champ de concentration. La turbulence est créée par une grille placée perpendiculairement à un écoulement uniforme à l'extérieur des couches limites qui se développent le long des parois de la veine d'essais à section carrée constante. L'écoulement de la présente étude est un écoulement d'eau, dans lequel le champ de concentration est celui d'une solution de Rhodamine B injectée au niveau de la grille à travers des injecteurs équi-répartis le long des barreaux de celle-ci. Ce choix, dicté par la technique de mesure du champ de concentration par Fluorescence Induite par Laser, permet en outre de mesurer le champ de vitesse par une autre technique optique, elle aussi non-intrusive. Pour se rapprocher le plus de la théorie d'un mélange idéal statistiquement homogène et isotrope sans vitesse moyenne, on considère dans l'expérience, conformément à l'hypothèse de Taylor, que toutes les échelles associées à chacun de ces champs, sont convectés à la vitesse moyenne U de l'écoulement, et l'on suit une "boîte de turbulence" qui se déplace à cette vitesse le long de la veine. Par suite déterminer l'état de la turbulence en un point donné de cette boite à l'instant t et à l'instant t'=t+dt, revient à l'étudier dans l'expérience à t à l'abscisse x de la veine d'essai, et à t' à l'abscisse x+dx , avec dx=Udt, où se trouve le point de la boîte aux deux instants successifs. Les résultats expérimentaux concernant les échelles pour lesquelles l'isotropie statistique est satisfaite, permettent alors de vérifier une phénoménologie de l'évolution de la cohérence temporelle des diverses échelles spatiales du champ des fluctuations de concentration fondée sur les idées de Comte-Bellot et Corrsin. Cette expérience, est en outre l'occasion de donner des résultats sur les densités de probabilité de diverses propriétés statistiques des champs de fluctuation de vitesse.
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Hýl, Petr. "Slovinské národní divadlo v Lublani." Master's thesis, Vysoké učení technické v Brně. Fakulta architektury, 2009. http://www.nusl.cz/ntk/nusl-215582.
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Taslimitehrani, Mojtaba. "Aspects of Gauge Theories in Lorentzian Curved Space-times." 2018. https://ul.qucosa.de/id/qucosa%3A32454.
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We study different aspects of perturbatively renormalized quantum gauge theories in the presence of non-trivial background Lorentzian metrics and background connections. First, we show that the proof of nilpotency of the renormalized interacting BRST charge can be reduced to the cohomological analysis of the classical BRST differential. This result guarantees the self-consistency of a class of local, renormalizable field theories with vanishing 'gauge anomaly'' at the quantum level, such as the pure Yang-Mills theory in four dimensions. Self-consistency here means that the algebra of gauge invariant observables can be constructed as the cohomology of this charge.
Second, we give a proof of background independence of the Yang-Mills theory. We define background independent observables in a geometrical formulation as flat sections of a cohomology algebra bundle over the manifold of background configurations, with respect to a flat connection which implements background variations. We observe that background independence at the quantum level is potentially violated. We, however, show that the potential obstructions can be removed by a finite renormalization.
Third, we construct the advanced/retarded Green's functions and Hadamard parametrices for linearized Yang-Mills and Einstein equations in general linear covariant gauges. They play an essential role in formulating gauge theories in curved spacetimes.
Finally, we study a superconformal gauge theory in three dimensions (the ABJM theory) which is conformally coupled to a curved background. The superconformal symmetry of this theory is described by a conformal symmetry superalgebra on manifolds which admit twistor spinors.
By analyzing the relevant cohomology class of an appropriate BV-BRST differential, we show that the full superalgebra is realized at the quantum level.
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Syue, You-Ming, and 薛又銘. "Spinor Formalism of Classical fields in four-dimensional Space-Times." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/45613323212935927835.
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碩士淡江大學
物理學系碩士班
102
This thesis is an introduction to the 2-spinor formalism. First we discuss the spinor algebra, and derive some important properties of the spinor space. Then, we consider some physical fields, and try to translate them into spinor form. In there, we choose the electromagnetic field, with classification in both the tensor and the spinor forms. After that we study the Weyl spinor and work out the algebraic type of the Schwarzschild solution.
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Jaireth, Subhash. "Theatre of the times of Socrates, Lunin and Nero : Time and space in Edvard Radzinskii’s trilogy ‘Theatre of the Times …’." Phd thesis, 1996. http://hdl.handle.net/1885/49343.
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This thesis attempts to unravel the nature of time in the trilogy and invokes Mikhail Bakhtin’s notion about the forms of time and the chronotope in literary narratives to do that. Bakhtinian concept of the chronotope provides a suitable strategy for reading a trilogy that aims to re-present ‘real’ time, place and human beings. The concept also provides a vantage point from where the trilogy can be read both from within the time-space of its main protagonists and from that of its author, readers, performers and spectators.
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Hackmann, Eva [Verfasser]. "Geodesic equations in black hole space-times with cosmological constant / von Eva Hackmann." 2009. http://d-nb.info/1002491398/34.
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McKeefry, Declan J., I. J. Murray, and Neil R. A. Parry. "Simple reaction times in colour space: the influence of chromaticity, contrast and cone opponency." 2003. http://hdl.handle.net/10454/2832.
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NoPURPOSE. This study examined the influence of stimulus chromaticity on simple reaction times (RTs) to determine the stage of chromatic processing that is most influential in their generation. METHODS. Simple RTs were measured in response to the cosinusoidally ramped onset of small, equiluminant, colored Gaussian spots. The chromaticity of these stimuli was varied, to modulate along a series of vectors in color space that included red-green (L-M) and blue-yellow (S-[L+M]) opponent axes. RESULTS. RTs are highly sensitive to small departures from subjective equiluminance. They are also dependent on stimulus chromaticity. The longest RTs are generated in response to equiluminant stimuli that isolate S-cone activity, whereas the shortest are generated by stimuli that modulate the L-M opponent axis. However, temporal processing differences are highly dependent on how the chromatic stimuli are scaled in relation to one another. The differences are reduced when scaling is based on detection threshold. The relationship between chromatic contrast and RT can be described by the modified Piéron equation RT = RT0 + k · C-1. CONCLUSIONS. Simple RTs generated in this study conform to the idea that they are largely determined by cone-opponency mechanisms. The use of cone contrast as a metric for scaling chromatic stimuli exaggerates differences between the temporal responsiveness of L-M and S-(L+M) opponency mechanisms.
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Harmsen, Gerhard Erwin. "Quasinormal modes for spin-3/2 particles in N-dimensional Schwarzschild black hole space times." Thesis, 2016. http://hdl.handle.net/10539/21023.
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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, June 2016.This dissertation will focus on spin-3/2 perturbations on N-dimensional Schwarzschild black holes, with the aim of calculating the numerical values for the quasi-normal modes (QNMs) and absorption probabilities associated with these perturbations. We begin by determining the spinor-vector eigenmodes of our particles on an (N-2)-dimensional spherical background. This allows us to separate out the angular part and radial part on our N-dimensional Schwarzschild metric. We then determine the equations of motion and e ective potential of our particles near the N-dimensional black hole. Using techniques such as the Wentzel-Kramers-Brillouin and Improved Asymptotic Iterative Method we determine our QNMs and absorption probabilities. We see that higher dimensional black holes emit QNMs with larger real and imaginary values, this would imply they emit higher energy particles but that these particles are highly dampened and therefore would be di cult to detect. The results of the QNMs make sense if we also consider the e ective potential surrounding our black holes with the potential function increasing with increasing number of dimensions.
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Wang, Yu-Hsiang, and 王昱翔. "Estimation of Time Varying Origin-Destination Trip Matrices by State Space Model with Travel Times." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/62580365751961105568.
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碩士國立交通大學
統計所
91
As origin-destination trip matrices becoming more and more important for many dynamic traffic network control and management analysis, approaches to estimate such matrices from traffic counts have attracted much research interest over the past decade. The dynamic origin-destination estimation approaches are relatively new. Their current status of development and applications are far from being as well recognized as those of static models. In this thesis we provide methods for estimating origin-destination demand pattern in the time domain. For doing this we consider the state space model with travel times to estimate parameters. These techniques rely on Gibbs sampler and Kalman filter. The model will also be extended to include non-Gaussian observation errors.
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Lipton, Briony. "Academic women in neoliberal times: Gender, time, space and emotion in the contemporary Australian university." Phd thesis, 2018. http://hdl.handle.net/1885/149066.
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The neoliberal transformation of higher education has a significant impact upon the careers of academic women. Despite women's inclusion across the organisational hierarchy, neoliberal new managerialism in Australian universities exacerbates gender inequity and inequitable practices in the way it redistributes power and reproduces and reinforces traditional gendered patterns of inequality. A focus on increased gender representation obscures the fact that women's participation continues to be measured and evaluated in relation to male norms of participation, and achievements and women remain largely invisible as academic leaders and respected knowledge producers.
This thesis is a feminist examination of key discourses, which constitute academic performativity and identity in the contemporary Australian university. In particular, how the discourses of neoliberalism and feminism are entangled in the structures, systems, operations, and cultures of the university, and how they constitute academic identity and performance. Drawing on in-depth qualitative interviews with academic women in Australia and critical autoethnography, this thesis uses a mix of experimental methods to emphasise the performative and discursive decisions women make in regard to their academic careers. This thesis takes inspiration from Helene Cixous' (1987) ecriture feminine and Sara Ahmed's (2014) concept of 'willfulness' as a methodological approach that playfully displaces gender and sex in scholarly research and writing and allows for a re-imagining of the academic self.