Variational Methods in AdS/CFT

We prove that the AdS/CFT calculation of 1-point functions can be drastically simplified by using variational arguments. We give a simple universal proof, valid for any theory that can be derived from a Lagrangian, that the large radius divergencies in 1-point functions can always be renormalized away (at least in the semiclassical approximation). The renormalized 1-point functions then follow by a simple variational problem involving only finite quantities. Several examples, a massive scalar, gravity, and renormalization flows, are discussed. Our results are general and can thus be used for dualities beyond AdS/CFT.Comment: 14 pages, no figures, LaTeX, minor change in footnot

Eddington-Born-Infeld action for dark energy and dark matter

We argue that Einstein gravity coupled to a Born-Infeld theory provides an attractive candidate to represent dark matter and dark energy. For cosmological models, the Born-Infeld field has an equation of state which interpolates between matter, w=0 (small times), and a cosmological constant w=-1 (large times). On galactic scales, the Born-Infeld field predicts asymptotically flat rotation curves.Comment: A sign mistake in section on galactic scales is pointed out. This sign invalidates the content of that section. See comment on manuscrip

Sensitivity of electromagnetically induced transparency to light-mediated interactions

Here we present a microscopic model that describes the Electromagnetically Induced Transparency (EIT) phenomenon in the multiple scattering regime. We consider an ensemble of cold three-level atoms, in a $\Lambda$ configuration, scattering a probe and a control field to the vacuum modes of the electromagnetic field. By first considering a scalar description of the scattering, we show that the light-mediated long-range interactions that emerge between the dipoles narrow the EIT transparency window for increasing densities and sample sizes. For a vectorial description, we demonstrate that near-field interacting terms can critically affect the atomic population transfer in the Stimulated Raman Adiabatic Passage (STIRAP). This result points out that standard STIRAP-based quantum memories in cold atomic ensembles would not reach high enough efficiencies for quantum information processing applications even in dilute regimes.Comment: 9 pages, 5 figure

Sistema de informação para rastreamento de pescado.

A rastreabilidade de peixes confere segurança para quem compra ou comercializa o pescado. Para que seja possível esta rastreabilidade ser usada pela sociedade, é necessário que exista algum repositório de dados que contenha, por exemplo, todo o histórico do pescado, tais como espécie, procedência, manejo, análise físico-química, biológica e microbiológica da água, características diversas relacionadas à carne e couro, e vários outros dados. Com isto, podem ser conhecidas várias características, incluindo a rastreabilidade, para se decidir sobre compra e venda de pescados de qualidade. Para atender a esta demanda, foi desenvolvido um sistema de informações de rastreabilidade relativas a diversos tipos de peixes; desta forma, o objetivo deste trabalho é demonstrar este sistema, que poderá ser usado livremente por qualquer usuário.ReCIP 2011

Constant Curvature Black Holes

Constant curvature black holes are constructed by identifying points in anti-de Sitter space. In n dimensions, the resulting topology is R^{n-1} * S_1, as opposed to the usual R^2 * S_{n-2} Schwarzschild black hole, and the corresponding causal structure is displayed by a (n-1)-dimensional picture, as opposed to the usual 2-dimensional Kruskal diagram. The five dimensional case, which can be embedded in a Chern-Simons supergravity theory, is analyzed in detail.Comment: New references added and some improvements in the presentation introduced, 5 pages, 2 eps figures, REVTe

Remarks on Resonant Scalars in the AdS/CFT Correspondence

The special properties of scalars having a mass such that the two possible dimensions of the dual scalar respect the unitarity and the Breitenlohner-Freedman bounds and their ratio is integral (``resonant scalars'') are studied in the AdS/CFT correspondence. The role of logarithmic branches in the gravity theory is related to the existence of a trace anomaly and to a marginal deformation in the Conformal Field Theory. The existence of asymptotic charges for the conformal group in the gravity theory is interpreted in terms of the properties of the corresponding CFT.Comment: 16 pages, 1 figur

Black Hole Entropy in the Chern-Simons Formulation of 2+1 Gravity

We examine Carlip's derivation of the 2+1 Minkowskian black hole entropy. A simplified derivation of the boundary action -valid for any value of the level k- is given.Comment: 6 pages, RevTeX, minor changes. Old title "Some remarks on Carlip's derivation of the 2+1 black hole entropy". Version to appear in Phys. Rev.

Anti-de Sitter space and black holes

Anti-de Sitter space with identified points give rise to black-hole structures. This was first pointed out in three dimensions, and generalized to higher dimensions by Aminneborg et al. In this paper, we analyse several aspects of the five dimensional anti-de Sitter black hole including, its relation to thermal anti-de Sitter space, its embedding in a Chern-Simons supergravity theory, its global charges and holonomies, and the existence of Killing spinors.Comment: 15 pages (twocolumn), 2 Postscript figure

Mass Generation and Symmetry Breaking in Chern-Simons Supergravity

We argue that the quartic fermionic potential of five-dimensional Chern-Simons supergravity induces spontaneous symmetry breaking, in a phenomenon bearing a close connection with the Nambu and Jona-Lasinio model.Comment: 5 pages, 1 eps figure. Corrected and added reference