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http://hdl.handle.net/10261/49
2016-05-27T10:20:37ZSolution-generating transformations and the string effective action
http://hdl.handle.net/10261/43094
Title: Solution-generating transformations and the string effective action
Authors: Bergshoeff, Eric A.; Jansen, Bert; Ortín Miguel, Tomás
Abstract: We study exhaustively the solution-generating transformations (dualities) that occur in the context of the low-energy effective action of superstring theory.
We first consider target-space duality (`T duality') transformations in the absence of vector fields. We find that for one isometry the full duality group is (SO↑(1, 1))3 × D4, the discrete part (D4) being non-Abelian. We then include non-Abelian Yang - Mills fields and find the corresponding generalization of the T duality transformations. We study the corrections to these transformations and show that the T duality rules are considerably simplified if the gauge group is embedded in the holonomy group.
Next, in the case in which there are Abelian vector fields, we consider the duality group that includes the transformation, introduced by Sen, that rotates among themselves the components of the metric, axion and vector field.
Finally we list the duality symmetries of the type II theories with one isometry.
Description: 23 páginas, 6 tablas.-- PACS numbers: 0465, 1125, 1130P.-- El Pdf del artículo es la versión pre-print: arXiv:hep-th/9506156v42011-12-05T08:48:20ZSL(2,R)-duality covariance of Killing spinors in axion-dilaton black holes
http://hdl.handle.net/10261/43074
Title: SL(2,R)-duality covariance of Killing spinors in axion-dilaton black holes
Authors: Ortín Miguel, Tomás
Abstract: Under SL(2,R) electric-magnetic duality transformations of the Bogomolnyi bound of dilaton-axion black holes is known to be invariant. In this paper we show that this invariance corresponds to the covariance of the N=4 supersymmetry transformation rules and their parameters. In particular this implies that Killing spinors transform covariantly into Killing spinors. As an example, we work out completely the case of the largest known family of axion-dilaton black holes which is SL(2,R) invariant, finding the Killing spinors with the announced properties.
Description: 5 páginas.-- El Pdf del artículo es su versión pre-print: arXiv:hep-th/9404035v12011-12-02T12:25:24ZSense and sensitivity of double beta decay experiments
http://hdl.handle.net/10261/42860
Title: Sense and sensitivity of double beta decay experiments
Authors: Gómez Cadenas, Juan José; Martín-Albo, Justo; Sorel, Michel; Ferrario, Paola; Monrabal, Francesc; Muñoz Vidal, Javier; Novella, Pau; Poves, Alfredo
Abstract: The search for neutrinoless double beta decay is a very active field in which the number of proposals for next-generation experiments has proliferated. In this paper we attempt to address both the sense and the sensitivity of such proposals. Sensitivity comes first, by means of proposing a simple and unambiguous statistical recipe to derive the sensitivity to a putative Majorana neutrino mass, mββ. In order to make sense of how the different experimental approaches compare, we apply this recipe to a selection of proposals, comparing the resulting sensitivities. We also propose a ``physics-motivated range'' (PMR) of the nuclear matrix elements as a unifying criterium between the different nuclear models. The expected performance of the proposals is parametrized in terms of only four numbers: energy resolution, background rate (per unit time, isotope mass and energy), detection efficiency, and ββ isotope mass. For each proposal, both a reference and an optimistic scenario for the experimental performance are studied. In the reference scenario we find that all the proposals will be able to partially explore the degenerate spectrum, without fully covering it, although four of them (KamLAND-Zen, CUORE, NEXT and EXO) will approach the 50 meV boundary. In the optimistic scenario, we find that CUORE and the xenon-based proposals (KamLAND-Zen, EXO and NEXT) will explore a significant fraction of the inverse hierarchy, with NEXT covering it almost fully. For the long term future, we argue that 136Xe-based experiments may provide the best case for a 1-ton scale experiment, given the potentially very low backgrounds achievable and the expected scalability to large isotope masses.
Description: El Pdf del artículo es la versión pre-print: arXiv:1010.5112v42011-11-28T14:36:16ZS duality and dyonic p-brane solutions in type II string theory
http://hdl.handle.net/10261/42769
Title: S duality and dyonic p-brane solutions in type II string theory
Authors: Bergshoeff, Eric A.; Ortín Miguel, Tomás
Abstract: We show how a solitonic ‘‘magnetically’’ charged p-brane solution of a given supergravity theory, with the magnetic charge carried by an antisymmetric tensor gauge field, can be generalized to a dyonic solution. We discuss the cases of ten-dimensional and eleven-dimensional supergravity in more detail and a new dyonic five-brane solution in ten dimensions is given. Unlike the purely electrically or magnetically charged five-brane solution the dyonic five-brane contains nonzero Ramond-Ramond fields and is, therefore, an intrinsically type II solution. The solution preserves half of the type II spacetime supersymmetries. It is obtained by applying a solution-generating SL(2,R)×SL(2,R) S duality transformation to the purely magnetically charged five-brane solution. One of the SL(2,R) duality transformations is basically an extension to the type II case of the six-dimensional Z2 string-string duality. We also present an action underlying the type IIB supergravity theory.
Description: 7 páginas.-- El Pdf del artículo es la versión pre-print: arXiv:hep-th/9508091v22011-11-24T14:17:02Z