Tesis Doctorado

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https://repositorio.udec.cl/handle/11594/201

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Browsing Tesis Doctorado by Author "Anabalón Dupuy, Andrés Fernando"

Now showing 1 - 5 of 5
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    Black holes and solitons in string theory and M-theory.
    (Universidad de Concepción, 2025) Oyarzo Catalán, Marcelo Andrés; Anabalón Dupuy, Andrés Fernando; Oliva Zapata, Julio Eduardo; Trigiante, Mario
    This thesis explores the effects of supersymmetry and higher-curvature corrections from superstring theory on black hole and soliton physics in different dimensions. The first order α′−corrections derived from heterotic string theory, up to a field redefinition, lead to Einstein-dilaton-Gauss-Bonnet theory. We construct the first-order correction of Schwarzschild black holes in arbitrary dimensions. In four dimensions, we show that the corrected backgrounds satisfy the first law of thermodynamics and allow the construction of slowly rotating black holes and accelerating black hole solutions in a perturbative approach. In five dimensions, we consider the α′-corrections to the black string background and the boosted black string. We construct the scalar perturbation of the metric field in the perturbative approach to assess the effect of α′ on the Gregory-Laflamme instability. We found that in the regime of validity of our approach, the instability window enlarges and grows with α′. In the context of the D = 5, N = 2 gauged STU model, we construct supersymmetric solitons, establishing new asymptotically locally AdS5 solutions with nontrivial boundary conditions for the gauge fields and their uplifts to type IIB supergravity. There exists a BPS limit for a specific relation between the boundary values of the gauge fields, leading to 1/8-BPS configurations. We study the phase diagram of this sector of the theory and found that, generally, there are two solitons for a given value of the boundary values of the gauge fields. Finally, we identify the states in supergravity that are dual to certain vacua in the dual field theory in the weak coupling and large N limit, labeled by the boundary conditions on the fields. This is done by computing the Casimir energy in the field theory in the weakly coupled limit and comparing it with the energy of the supergravity solution. The four-dimensional STU model in maximal gauged supergravity is studied for static electric and magnetic black holes with general horizon geometries. Thermodynamic stability analysis reveals unstable electric black holes for temperatures below certain value, including Reissner-Nordström. While magnetic BPS black holes demonstrate quasi stability. We find extremal non-BPS black holes, which are thermodynamically unstable. These results deepen the understanding of the interplay between string-inspired corrections, black hole physics, and supersymmetric stability criteria in different dimensions.
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    Consequences of Torsion in Four Dimensions.
    (Universidad de Concepción, 2024) Medina Medina, Perla Soledad; Anabalón Dupuy, Andrés Fernando
    This thesis addresses two fundamental topics in the field of gravity. First, a reformulation of the Mimetic theory of gravity in first-order formalism for differential forms, i.e., the mimetic version of Einstein-Cartan-Kibble-Sciama (ECKS) gravity. Here we consider different possibilities on how torsion is af- fected by conformal transformations and discuss how this translates into the interpolation between two different conformal transformations of the spin con- nection, parameterized with a zero-form parameter λ. We prove that regardless of the type of transformation one chooses, in this setting torsion remains as a non-propagating field. We also discuss the conservation of the mimetic stress- energy tensor and show that the trace of the total stress-energy tensor is not null but depends on both, the value of λ and spacetime torsion. Second, the Einstein-Hilbert action is studied in the first-order formalism, considering the coupling of a scalar field to different topological invariants. The implications of this coupling on the dynamics of the gravitational field and the evolution of the early universe are analyzed. The results obtained contribute to a better understanding of gravity and its relationship with the topology of spacetime. Second, the Einstein-Hilbert action is studied in the first-order formalism, con- sidering the coupling of a scalar field to different topological invariants. The implications of these couplings on the field equations are analyzed. The re- sults obtained shed light on a theoretical framework where it could be easier to introduce couplings of scalar fields to the geometry.
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    Lorentz and diffeomorphism violation in efective theories of gravity and matter.
    (Universidad de Concepción, 2025) Riquelme Durán, César Emanuel; Reyes Martínez, Carlos Marat; Anabalón Dupuy, Andrés Fernando
    En la presente tesis se estudió en profundidad el sector minimal de la extensión del Modelo Estándar Gravitacional (gSME) en un escenario cosmológico, con el objetivo de desvelar las condiciones de compatibilidad entre los campos background y la dinámica de la teoría. Para ello, se analizó el rompimiento explícito y espontáneo de la invariancia bajo difeomorfismos de la Relatividad General dentro del marco de las teorías efectivas. En ambos casos se derivaron las ecuaciones de Friedmann modificadas, así como las configuraciones requeridas por los campos de background para preservar la isotropía y la homogeneidad. En este contexto, se identificaron configuraciones que permiten multiples fases de expansión del universo. Este estudio condujo al desarrollo de un método para tratar las incompatibilidades entre las violaciones explícitas de difeomorfismos y la geometría Riemanniana, basado en el análisis de las isometrías de un sistema gravitacional. Se concluye que las configuraciones de los campos de background son más propensas a determinarse cuanto mayor sea el número de difeomorfismos que actúan como isometrías del sistema en el caso de rompimiento explícito; en cambio, en el caso de rompimiento espontáneo, el campo de background no requiere respetar dichas isometrías para garantizar la compatibilidad. Prueba de la efectividad del método, se logra estudiar violaciones de causalidad en presencia de campos de background de forma consistente.
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    Raices Topológicas de la Gravedad en cuatro dimensiones.
    (Universidad de Concepción, 2007) Anabalón Dupuy, Andrés Fernando; Zanelli, Jorge
    La posibilidad de definir Lagrangeanos gravitacionales usando formas de gauged Wess-Zumino-Witten es explorada. Primeramente se discuten ejemplos mecánicos simples que permiten familiarizarse con los Lagrangeanos tipo Wess-Zumino-Witten. Se hace manifiesta la conexión de estas estructuras con Lagrangeanos gravitacionales en más dimensiones, así como con la teoría de Einstein en cuatro dimensiones. Las ecuaciones de movimiento, de la teoría basada en la forma de gauged Wess-Zumino-Witten en cuatro dimensiones son escritas, y estudiadas, por primera vez. Relaciones off-shell entre ellas son encontradas y usadas para simplificar y discutir la teoría.
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    The thermodynamic role of solitons in the phase space of (super)gravity.
    (Universidad de Concepción, 2024) Quijada Barrera, Constanza del Pilar; Oliva Zapata, Julio Eduardo; Anabalón Dupuy, Andrés Fernando
    In this thesis we study the phase transitions between the planar charged black hole and the charged AdS soliton, which are solutions to the Einstein-AdS theory coupled to linear and non-linear electrodynamics theory. The analysis is carried out in the grand canonical ensemble. The charged planar soliton is obtained as a double analytic continuation of the charged black hole metric, which also involves analytically continuing the electric charge, therefore it appears a magnetic charge on the soliton solution which is associated with a magnetic flux along the non-cyclic planar coordinate. In the case of Einstein-Maxwell theory with negative cosmological constant, we show that there are phase transitions between both solutions depending on the values of electric potential, magnetic flux and temperature. On the other hand, when it is considered the gravitational theory coupled to a non-linear electrodynamics, we show that the phase space of the theory is very rich, containing reen trant phase transitions, as well as triple points, for small values of the coupling controlling the non-linearity of the electrodynamics Lagrangian.
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