Braneworlds, Conformal Fields and the Gravitons

We investigate the dynamics of Randall-Sundrum AdS5 braneworlds with 5-dimensional conformal matter fields. In the scenario with a compact fifth dimension the class of conformal fields with weight -4 is associated with exact 5-dimensional warped geometries which are stable under radion field perturbations and describe on the brane the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytropic dark energy. We analyse the graviton mode flutuations around this class of background solutions and determine their mass eigenvalues and wavefunctions from a Sturm-Liouville problem. We show that the localization of gravity is not sharp enough for large mass hierarchies to be generated. We also discuss the physical bounds imposed by experiments in particle physics, in astrophysics and in precise measurements of the low energy gravitational interaction.Comment: LaTeX, 9 pages, 2 figures. Based on talk given in the Second International Conference on Quantum Theories and the Renormalization Group in Gravity and Cosmology, CSIC and University of Barcelona, Barcelona, Spain, 11-15 July 2006. Submitted to be published in the Conference Proceedings, J. Phys. A: Math. Ge

Constraining the tidal charge of brane black holes using their shadows

A constraint on the tidal charge generated within a brane world is shown. Using the shadow of a rotating black hole in a brane context in order to describe the M87* parameters recently announced by the Event Horizon Telescope Collaboration, the deviation from circularity of the reported shadow produces an upper bound on the bulk's nonlocal effect, which is conceived of as a tidal charge in the four-dimensional brane induced by the five-dimensional bulk. Therefore, a deviation from circularity $\lesssim 10\%$ leads to an upper bound on the tidal charge $\lesssim 0.004M^2$.Comment: 9 pages, 2 figures, 1 table. V2 with minor changes and new references. Published in The European Physical Journal

Nietzsche for physicists

One of the most important philosophers in history, the German Friedrich Nietzsche, is almost ignored by physicists. This author who declared the death of God in the 19th century was a science enthusiast, especially in the second period of his work. With the aid of the physical concept of force, Nietzsche created his concept of will to power. After thinking about energy conservation, the German philosopher had some inspiration for creating his concept of eternal recurrence. In this article, some influences of physics on Nietzsche are pointed out, and the topicality of his epistemological position$-$the perspectivism$-$is discussed. Considering the concept of will to power, I propose that the perspectivism leads to an interpretation where physics and science in general are viewed as a game.Comment: 14 pages. Version 3 with improvements, corrections. Accepted in Philosophia Scientia

Wormholes in de Sitter branes

In this work we present a class of geometries which describes wormholes in a Randall-Sundrum brane model, focusing on de Sitter backgrounds. Maximal extensions of the solutions are constructed and their causal structures are discussed. A perturbative analysis is developed, where matter and gravitational perturbations are studied. Analytical results for the quasinormal spectra are obtained and an extensive numerical survey is conducted. Our results indicate that the wormhole geometries presented are stable.Comment: 10 pages, 7 figure