Lie-algebra expansions, Chern-Simons theories and the Einstein-Hilbert lagrangian

Starting from gravity as a Chern-Simons action for the AdS algebra in five dimensions, it is possible to deform the theory through an expansion of the Lie algebra that leads to a system consisting of the Einstein-Hilbert action plus nonminimally coupled matter. The deformed system is gauge invariant under the Poincare group enlarged by an Abelian ideal. Although the resulting action naively looks like General Relativity plus corrections due to matter sources, it is shown that the nonminimal couplings produce a radical departure from GR. Indeed, the dynamics is not continuously connected to the one obtained from Einstein-Hilbert action. In a matter-free configuration and in the torsionless sector, the field equations are too strong a restriction on the geometry as the metric must satisfy both the Einstein and pure Gauss-Bonnet equations. In particular, the five-dimensional Schwarzschild geometry fails to be a solution; however, configurations corresponding to a brane-world with positive cosmological constant on the worldsheet are admissible when one of the matter fields is switched on. These results can be extended to higher odd dimensions.Comment: 11 page

Vacuum solutions with nontrivial boundaries for the Einstein-Gauss-Bonnet theory

The classification of certain class of static solutions for the Einstein-Gauss-Bonnet theory in vacuum is presented. The spacelike section of the class of metrics under consideration is a warped product of the real line with a nontrivial base manifold. For arbitrary values of the Gauss-Bonnet coupling, the base manifold must be Einstein with an additional scalar restriction. The geometry of the boundary can be relaxed only when the Gauss-Bonnet coupling is related with the cosmological and Newton constants, so that the theory admits a unique maximally symmetric solution. This additional freedom in the boundary metric allows the existence of three main branches of geometries in the bulk, containing new black holes and wormholes in vacuum.Comment: Prepared for the proceedings of the 7th Alexander Friedmann International Seminar on Gravitation and Cosmology, July 2008, Joao Pessoa, Brasil. 4 pages, References adde

Higher Dimensional Gravity, Propagating Torsion and AdS Gauge Invariance

The most general theory of gravity in d-dimensions which leads to second order field equations for the metric has [(d-1)/2] free parameters. It is shown that requiring the theory to have the maximum possible number of degrees of freedom, fixes these parameters in terms of the gravitational and the cosmological constants. In odd dimensions, the Lagrangian is a Chern-Simons form for the (A)dS or Poincare groups. In even dimensions, the action has a Born-Infeld-like form. Torsion may occur explicitly in the Lagrangian in the parity-odd sector and the torsional pieces respect local (A)dS symmetry for d=4k-1 only. These torsional Lagrangians are related to the Chern-Pontryagin characters for the (A)dS group. The additional coefficients in front of these new terms in the Lagrangian are shown to be quantized.Comment: 10 pages, two columns, no figures, title changed in journal, final version to appear in Class. Quant. Gra

Calculation of the calibration factors for witch flounder and squid from the comparative experience between the R/V Cornide de Saavedra and the R/V Vizconde de Eza in Flemish Cap in 2003 and 2004.

EU carries out a stratified random summer bottom trawl survey in Flemish Cap, Division 3M of the NAFO Regulatory Area, since 1988. Since 1991, the survey was made with the R/V Cornide de Saavedra. In 2003, this vessel was replaced for the R/V Vizconde de Eza, so, in order to maintain the series obtained from the old vessel, a two year comparative fishing trial between the two vessels was made in the years 2003 and 2004. This work presents the methods used for the transformation of the series and their results for biomass and length distribution for two species in the area: witch flounder and squid. For both species, the R/V Vizconde de Eza is more efficient that the R/V Cornide de Saavedra for the biomass, with values of FPC equal to 1.7573 in the case of the witch flounder and 1.2792 in the case if the squid. Witch flounder biomass and abundance are very fluctuating, especially since 2003, with the change of vessel, and in general, small individuals are not present during the survey. For squid the biomass and abundance are low except for years 1991, 1992, 2006 and 2008. In 2013 and 2015, no catches were reported during the survey. All the numbers are very poor in general.Postprint0,000

Simple compactifications and Black p-branes in Gauss-Bonnet and Lovelock Theories

We look for the existence of asymptotically flat simple compactifications of the form $M_{D-p}\times T^{p}$ in $D$-dimensional gravity theories with higher powers of the curvature. Assuming the manifold $M_{D-p}$ to be spherically symmetric, it is shown that the Einstein-Gauss-Bonnet theory admits this class of solutions only for the pure Einstein-Hilbert or Gauss-Bonnet Lagrangians, but not for an arbitrary linear combination of them. Once these special cases have been selected, the requirement of spherical symmetry is no longer relevant since actually any solution of the pure Einstein or pure Gauss-Bonnet theories can then be toroidally extended to higher dimensions. Depending on $p$ and the spacetime dimension, the metric on $M_{D-p}$ may describe a black hole or a spacetime with a conical singularity, so that the whole spacetime describes a black or a cosmic $p$-brane, respectively. For the purely Gauss-Bonnet theory it is shown that, if $M_{D-p}$ is four-dimensional, a new exotic class of black hole solutions exists, for which spherical symmetry can be relaxed. Under the same assumptions, it is also shown that simple compactifications acquire a similar structure for a wide class of theories among the Lovelock family which accepts this toroidal extension. The thermodynamics of black $p$-branes is also discussed, and it is shown that a thermodynamical analogue of the Gregory-Laflamme transition always occurs regardless the spacetime dimension or the theory considered, hence not only for General Relativity. Relaxing the asymptotically flat behavior, it is also shown that exact black brane solutions exist within a very special class of Lovelock theories.Comment: 30 pages, no figures, few typos fixed, references added, final version for JHE

Results for capelin from the surveys conducted by Spain in the NAFO Regulatory Area of Div. 3NO, 1995-2015

Since 1995, a stratified random spring bottom trawl survey in the NAFO Regulatory Area of Div. 3NO has been conducted by Spain every year. In 2001, the trawl vessel was replaced in the realization of the survey; a comparative survey between both vessels was made to transform the historical time-series into the new vessel index. The transformed entire series of mean catches and biomass distribution for capelin (Mallotus villosus) are presented for the period 1995-2000, and the no-transformed data for the years 2002-2015. In 2001, there are data from both vessels. The standard deviation is shown for biomass. Biomass fluctuated during all the period, and peaked in 2012.Postprint0,000

Quality of the Surveys Information in Relation with the Greenland Halibut Assessment of Subarea 2 and Divisions 3KLMNO

The aim of this paper is to provide a study of the quality of the surveys information in relation with the Greenland halibut assessment of the NAFO Subarea 2 and Divisions 3KLMNO. The surveys abundance correlation within surveys, between surveys and XSA showed that the surveys had many difficulties to track ages older than 6 years. For Flemish Cap survey and Canadian Spring Survey, the problem to track these ages could be principally the depth coverage of the surveys, but for the other surveys this lack of tracking could be due to different reasons as age reading inconsistencies and changes in catchability of these ages in the surveys

Report of the NAFO Joint Commission-Scientific Council Working Group on Risk-Based Management Strategies (WG-RBMS) Meeting

The meeting was opened by the co-Chairs Fernando González-Costas (European Union) and Ray Walsh (Canada) at 09:30 hours (UTC/GMT -3 hours in Halifax, Nova Scotia) on Wednesday, 17 August 2022

Supersymmetry of gravitational ground states

A class of black objects which are solutions of pure gravity with negative cosmological constant are classified through the mapping between the Killing spinors of the ground state and those of the transverse section. It is shown that these geometries must have transverse sections of constant curvature for spacetime dimensions d below seven. For d > 6, the transverse sections can also be Euclidean Einstein manifolds. In even dimensions, spacetimes with transverse section of nonconstant curvature exist only in d = 8 and 10. This classification goes beyond standard supergravity and the eleven dimensional case is analyzed. It is shown that if the transverse section has negative scalar curvature, only extended objects can have a supersymmetric ground state. In that case, some solutions are explicitly found whose ground state resembles a wormhole.Comment: 16 pages, CECS style, minor correction