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Aspects of the AdS/CFT correspondence in less supersymmetric backgrounds
No full textIn this thesis we study the AdS/CFT correspondence in backgrounds with less supersymmetry. We consider AdS_5 x T {1,1} whose correspondence to N=1 gauge theory is known as the Klebanov-Witten model. We also consider real [beta]-deformations, often called [gamma]-deformations which are exactly marginal deformations of the gauge theory. Their supergravity duals can be found by a solution generating technique of Lunin and Maldacena.We use (semi)classical approach and consider solutions of particular shape, the circular and folded spinning string, giant magnon and single spike. We focus on dispersion relations which are supposed to give the anomalous dimensions and three-point correlation functions at strong coupling. In a sector of [gamma]-deformed conifold we find giant magnon and single spike string solutions. We examine the dispersion relations and find a behavior analogous to the undeformed case. The transcendental functional relations between the conserved charges are shifted by certain [gamma]-dependent term. The latter is proportional to the total momentum and thus qualitatively different from known cases. In the analysis of the finite size corrections we find a leading and a subleading contribution in the first order approximation. This behavior is different from the known case of AdS_5 x S 5.In the study of the correlation functions at strong coupling we used a recent method, that allows to consider three-point functions of operators corresponding to two heavy string states and a light supergravity state. We used several string solutions with one and two spins in the T {1,1} part of the geometry. The three-point functions we obtained for both, the single spin and the two spin case, are given implicitly, due to transcendental relations between conserved charges.We also check the consistency of the structure constants of the correlators with those obtained from 2\pi {2}a_{\mathcal{L}AA}=\lambda\partial E/\partial\lambda and find complete agreement
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Wie allgemein ist Holographie?
Get PDF"Wie allgemein ist das holographische Prinzip?- Dieser Frage werde ich mich in meiner Dissertation widmen. Sie ist von so fundamentaler Natur, dass es sinnvoll erscheint, sich diesem Problem in einer Umgebung zu stellen, die möglichst simpel, aber dennoch interessant und komplex genug ist, um generelle Aussagen tätigen zu können. Da Gravitation in 2+1 Dimensionen diesen Anforderungen entspricht, werde ich mich auf Holographie konzentrieren, deren Gravitationstheorien 2+1 Dimensionen und deren Quantenfeldtheorien 1+1 Dimensionen aufweisen. Die zwei wichtigsten Gründe hierfür sind, dass (i) Gravitation in 2+1 Dimensionen technisch sehr effizient beschrieben werden kann, und (ii) dass die dualen Quantenfeldtheorien unendlich viele Symmetrien haben und somit einen sehr hohen Grad an Kontrolle erlauben. Dies ermöglicht es, neuartige holographische Korrespondenzen exakt zu überprüfen. Von speziellem Interesse, was die allgemeine Gültigkeit des holographischen Prinzips betrifft, sind so genannte Höhere-Spin-Gravitationstheorien, welche die übliche lokale Koordinateninvarianz mit weiteren verallgemeinerten Symmetrien erweitern. Zunächst beschäftige ich mich mit Höherer-Spin-Holographie, die auf Raumzeiten basiert, welche nicht asymptotisch Anti-de-Sitter sind. Von einer gegebenen Gravitationstheorie ausgehend, bestimme ich in weiterer Folge die dazugehörigen asymptotischen Symmetrien der dualen Quantenfeldtheorien und unitäre Repräsentationen dieser Symmetriealge- bren. Weiters beschreibe ich eine Möglichkeit, im Rahmen dieser "nicht-Anti-de-Sitter- Holographie" eine duale Quantenfeldtheorie zu erhalten, welche eine beliebig große (aber nicht unendliche) Anzahl von Quantenzuständen zulässt. Der zweite Teil dieser Dissertation beschäftigt sich mit Holographie für asymptotisch flache Raumzeiten. Zuerst zeige ich, wie man verschiedene Ergebnisse, wie zum Beispiel eine (Höhere-Spin) Cardy-Formel für flache Raumzeiten, welche die Anzahl der Quan- tenzustände einer konformen Feldtheorie bei einer bestimmten Temperatur angibt, oder die asymptotischen Symmetrien von asymptotisch flachen Raumzeiten als Limes einer verschwindenden kosmologischen Konstante der bekannten Anti-de-Sitter-Ergebnisse er- halten kann. Weiters setze ich mich mit unitären Repräsentationen der asymptotischen Symmetrieal- gebren von asymptotisch flachen Raumzeiten auseinander. Dies führt unter bestimmten Annahmen zu einem NO-GO-Theorem, welches nicht gleichzeitig flache Raumzeiten, Höhere-Spin-Symmetrien und Unitarität erlaubt. Ebenso wird eine Möglichkeit, dieses NO-GO-Theorem zu umgehen, explizit behandelt. Überdies werde ich zeigen, wie man asymptotisch flache Raumzeiten inklusive (Höhere- Spin) chemischer Potentiale holographisch konsistent beschreiben kann. Ebenso werde ich die dazugehörige thermale Entropie von bestimmten kosmologischen asymptotisch flachen Raumzeiten bestimmen. Den Schluss meiner Dissertation bildet eine explizite Überprüfung des holographischen Prinzips für asymptotisch flache Raumzeiten. Ich präsentiere eine Methode, die eine bestimmte Form einer Wilson-Schleife darstellt, welche eine holographische Bestimmung der Verschränkungsentropie von Feldtheorien erlaubt, von denen angenommen wird, dual zu asymptotisch flachen Raumzeiten zu sein. Ich erweitere die Methode überdies, um auch erfolgreich Höhere-Spin-Symmetrie miteinzubeziehen und die thermale Entropie der zugehörigen dualen Feldtheorien bestimmen zu können."How general is the holographic principle?- This is the question I will explore in this thesis. As this question is very fundamental, one is well advised to try and tackle the problem in an environment which is as simple as possible but still interesting and complex enough to allow for a general interpretation of the results. Since gravity in 2+1 dimensions satisfies those requirements I will focus on holography involving 2+1 dimensional spacetimes and 1+1 dimensional quantum field theories. The two most important reasons for this are: (i) gravity in 2+1 dimensions can be described very efficiently on a technical level. (ii) The dual quantum field theories have infinitely many symmetries and thus allow for a very high degree of control. This allows one to explicitly and exactly check new holographic correspondences. Of very special interest regarding the generality of the holographic principle are so-called higher-spin gravity theories which extend the usual local invariance under coordinate changes by a more general set of symmetries. In this thesis I will first focus on higher-spin holography which is based on spacetimes that do not asymptote to Anti-de Sitter spacetimes. Starting from a given higher-spin theory I will determine the corresponding asymptotic symmetries of the corresponding dual quantum field theories and their unitary representations. Furthermore, using "non-Anti-de Sitter holography" I will describe a dual quantum field theory, which allows for an arbitrary (albeit not infinitely) large number of quantum microstates. The second part of this thesis is concerned with holography for asymptotic flat spacetimes. First I will show how to obtain various results, like an analogue of a (higher-spin) Cardy formula which counts the number of microstates of a conformal field theory at a given temperature, or the asymptotic symmetries of asymptotically flat spacetimes, as a limit of vanishing cosmological constant from the known Anti-de Sitter results. Furthermore, I will explore unitary representations of the asymptotic symmetry algebras of asymptotically flat spacetimes, which under certain assumptions, will result in a NO-GO theorem that forbids having flat space, higher-spins and unitarity at the same time. In addition I will elaborate on a specific example that allows to circumvent this NO-GO theorem. I will also show how to consistently describe asymptotically flat spacetimes with additional (higher-spin) chemical potentials in a holographic setup and how to determine the corre- sponding thermal entropy of certain cosmological asymptotically flat spacetimes. The finale of this thesis will be an explicit check of the holographic principle for asymp- totically flat spacetimes. I will present a method, using a special version of a Wilson-line, which allows one to determine the entanglement entropy of field theories which are assumed to be dual to asymptotically flat spacetimes in a holographic manner. I will also extend this method in order to be able to also successfully include higher-spin symmetries and determine the thermal entropy of the corresponding dual field theories
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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