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Five-dimensional gravitational brane-world models: Solutions for black strings and black holes

In the context of this dissertation, we study the emergence of black-string and black-hole solutions in the framework of five-dimensional braneworld models. The main motivation for studying such theories stems from the Randall-Sundrum model, which was formulated by Lisa Randall and Raman Sundrum back in 1999. We investigate thoroughly the physical characteristics of analytic solutions which concern both black strings and five-dimensional localized black holes. To be more precise, the black-string solutions emerge in the context of a five-dimensional scalar-tensor theory, where the brane line-element is found to describe a Schwarzschild-(anti-)de Sitter spacetime. The cases of de Sitter, anti-de Sitter and Minkowski branes are examined separately and in great detail. As far as the five-dimensional black holes are concerned, at first, we present an "algorithm" that one may use in order to construct from first principles the geometry of analytic and exponentially localized five-dimensional braneworld black holes. In each case, the point-like singularity of the black hole lies entirely on the 3-brane, while its event horizon is exponentially localized close to the 3-brane thus exhibiting a pancake shape. In the first case, the induced line-element on the brane assumes the form of the Schwarzschild solution while the bulk geometry is effectively AdS$_5$ outside the horizon. In the second case, the induced brane geometry is described by the Reissner-Nordström-(A)dS line-element, where a careful classification of the horizons takes place as well. In both cases, the derived geometry is supported by an anisotropic fluid in the bulk described only by two independent components, the energy density and tangential pressure, whereas no matter needs to be introduced on the brane for its consistent embedding in the bulk.