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The Global ETD Search service is a free service for researchers
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 21 to 22 of 22 (0.031 seconds)Spelling suggestions: "subject:"btheory"" "subject:"bytheory""
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Dualities, Symmetries and Unbroken Phases in String Theory : Probing the Composite Nature of the String / Dualiteter, Symmetrier och Obrutna Faser i Strängteori : En Utforskning av Strängens Sammansatta NaturEngquist, Johan January 2005 (has links)
The thesis treats aspects of string/M-theory in anti-de Sitter spacetimes and their supersymmetric completions. By applying the AdS/CFT correspondence, as well as models of spin chains and singletons, we try to attain a better understanding of the underlying symmetries and the unbroken phases of string/M-theory. Tensionless string/M-theory in anti-de Sitter spacetime is argued to imply a higher spin gauge symmetry enhancement and to be described by gauged sigma models of multi-singletons as well as by closed singleton strings. Vasiliev's weakly projected equations of symmetric massless higher spin gauge fields in the vector oscillator formulation is shown to follow from a deformation of the singleton model. Various four dimensional minimal as well as non-minimal supersymmetric higher spin gauge theories in the spinor formulation are examined. The minimal higher spin gauge theory based on the symmetry algebra hs(1|4) is elaborated on in an N=1 superspace, illustrating the remarkable fact that the choice of base manifold is not fixed in unfolded dynamics. The importance of the representations saturating the unitarity bounds in anti-de Sitter spacetime is stressed throughout the thesis, with particular emphasis on the singleton and the massless representations. Singletons, and hence massless states, are shown to appear as bound states on the string or p-brane and are localized at cusps. Furthermore, we examine semiclassical string solutions in Type IIB String Theory in AdS(5) x S(5) and their boundary duals in N=4 Super Yang-Mills Theory in d=4 which are constituted out of thermodynamic composite operators. By using integrable spin chain techniques and Bäcklund transformations in the field theory and in the string theory, respectively, the one-loop anomalous dimensions as well as the tower of conserved charges of the composite operators are shown to be in agreement with the energies and the tower of conserved charges associated with the dual string states.
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Field Theoretic Lagrangian From Off-shell Supermultiplet Gauge QuotientsKatona, Gregory 01 January 2013 (has links)
Recent efforts to classify off-shell representations of supersymmetry without a central charge have focused upon directed, supermultiplet graphs of hypercubic topology known as Adinkras. These encodings of Super Poincare algebras, depict every generator of a chosen supersymmetry as a node-pair transformtion between fermionic bosonic component fields. This research thesis is a culmination of investigating novel diagrammatic sums of gauge-quotients by supersymmetric images of other Adinkras, and the correlated building of field theoretic worldline Lagrangians to accommodate both classical and quantum venues. We find Ref [40], that such gauge quotients do not yield other stand alone or "proper" Adinkras as afore sighted, nor can they be decomposed into supermultiplet sums, but are rather a connected "Adinkraic network". Their iteration, analogous to Weyl's construction for producing all finite-dimensional unitary representations in Lie algebras, sets off chains of algebraic paradigms in discrete-graph and continuous-field variables, the links of which feature distinct, supersymmetric Lagrangian templates. Collectively, these Adiankraic series air new symbolic genera for equation to phase moments in Feynman path integrals. Guided in this light, we proceed by constructing Lagrangians actions for the N = 3 supermultiplet YI /(iDI X) for I = 1, 2, 3, where YI and X are standard, Salam-Strathdee superfields: YI fermionic and X bosonic. The system, bilinear in the component fields exhibits a total of thirteen free parameters, seven of which specify Zeeman-like coupling to external background (magnetic) fluxes. All but special subsets of this parameter space describe aperiodic oscillatory responses, some of which are found to be surprisingly controlled by the golden ratio, [phi] = 1.61803, Ref [52]. It is further determined that these Lagrangians allow an N = 3 - > 4 supersymmetric extension to the Chiral-Chiral and Chiral-twistedChiral multiplet, while a subset admits two inequivalent such extensions. In a natural proiii gression, a continuum of observably and usefully inequivalent, finite-dimensional off-shell representations of worldline N = 4 extended supersymmetry are explored, that are variate from one another but in the value of a tuning parameter, Ref [53]. Their dynamics turns out to be nontrivial already when restricting to just bilinear Lagrangians. In particular, we find a 34-parameter family of bilinear Lagrangians that couple two differently tuned supermultiplets to each other and to external magnetic fluxes, where the explicit parameter dependence is unremovable by any field redefinition and is therefore observable. This offers the evaluation of X-phase sensitive, off-shell path integrals with promising correlations to group product decompositions and to deriving source emergences of higher-order background flux-forms on 2-dimensional manifolds, the stacks of which comprise space-time volumes. Application to nonlinear sigma models would naturally follow, having potential use in M- and F- string theories.
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