Examinando por Autor "Merino, Nelson"

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    Black hole solutions in Chern-Simons AdS supergravity
    (Springer Verlag, 2014-08) Giribet, Gaston; Merino, Nelson; Miskovic, Olivera; Zanelli, Jorge
    We study charged AdS black hole solutions in five-dimensional Chern-Simons supergravity. The minimal supergroup containing such AdS5 × U(1) configurations is the superunitary group SU(2, 2|N ). For this model, we find analytic black hole solutions that asymptote to locally AdS5 spacetime at the boundary. A solution can carry U(1) charge provided the spacetime torsion is non-vanishing. Thus, we analyze the most general config uration consistent with the local AdS5 isometries in Riemann-Cartan space. The coupling of torsion in the action resembles that of the universal axion of string theory, and it is ulti mately due to this field that the theory acquires propagating degrees of freedom. Through a careful analysis of the canonical structure the local degrees of freedom of the theory are identified in the static symmetric sector of phase space.
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    Einstein-Gauss-Bonnet theory of gravity: The Gauss-Bonnet-Katz boundary term
    (American Physical Society, 2018-05) Deruelle, Nathalie; Merino, Nelson; Olea, Rodrigo
    We propose a boundary term to the Einstein-Gauss-Bonnet action for gravity, which uses the Chern-Weil theorem plus a dimensional continuation process, such that the extremization of the full action yields the equations of motion when Dirichlet boundary conditions are imposed. When translated into tensorial language, this boundary term is the generalization to this theory of the Katz boundary term and vector for general relativity. The boundary term constructed in this paper allows to deal with a general background and is not equivalent to the Gibbons-Hawking-Myers boundary term. However, we show that they coincide if one replaces the background of the Katz procedure by a product manifold. As a first application we show that this Einstein Gauss-Bonnet Katz action yields, without any extra ingredients, the expected mass of the Boulware-Deser black hole. © 2018 American Physical Society.
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    First-order Lagrangian of Lovelock gravity and applications
    (Universidad Andrés Bello, 2022) Guilleminot Arellano, Pablo; Olea, Rodrigo; Merino, Nelson; Faraggi, Alberto; Miskovic, Olivera; Aros, Rodrigo; Corral, Cristóbal; Facultad de Ciencias Exactas
    En este trabajo, se analizan, analíticamente, aspectos de evolución espacial en gravedad de Lovelock. Se muestra que la adición de términos de Myers a la acción elimina las derivadas de segundo orden respecto a la variable de evolución. Así, la conexión entre el problema de Dirichlet y Lagrangianos de primer orden es establecida. Luego, se exhibe como la transformada de Legendre de este último permite calcular directamente el Hamiltoniano del sistema para la misma variable de evolución. Con estos resultados, se analiza el comportamiento de cáscaras delgadas con masa en el contexto de gravedad de Lovelock. Para esto, se trabaja el principio variacional escrito en un set adaptado de coordenadas válido cerca de la cáscara. Se concluye que la cantidad que es discontínua en la cáscara es el momentum canónico. Finalmente se obtienen algunas expresiones explicitas para configuraciones con simetría esférica.
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    Thin shell dynamics in Lovelock gravity
    (Institute for Ionics, 2022-11) Guilleminot, Pablo; Merino, Nelson; Olea, Rodrigo
    We study matching conditions for a spherically symmetric thin shell in Lovelock gravity which can be read off from the variation of the corresponding first-order action. In point of fact, the addition of Myers’ boundary terms to the gravitational action eliminates the dependence on the acceleration in this functional and such that the canonical momentum appears in the surface term in the variation of the total action. This procedure leads to junction conditions given by the discontinuity of the canonical momentum defined for an evolution normal to the boundary.In particular, we correct existing results in the literature for the thin shell collapse in generic Lovelock theories, which were mistakenly drawn from an inaccurate analysis of the total derivative terms in the system. © 2022, The Author(s).