Extreme objects with arbitrary large mass, or density, and arbitrary size

We consider a generalization of the interior Schwarzschild solution that we match to the exterior one to build global C^1 models that can have arbitrary large mass, or density, with arbitrary size. This is possible because of a new insight into the problem of localizing the center of symmetry of the models and the use of principal transformations to understand the structure of space.Comment: 20 pages, 6 figures. Fixed one reference. Added a new equatio

Comparing metrics at large: harmonic vs quo-harmonic coordinates

To compare two space-times on large domains, and in particular the global structure of their manifolds, requires using identical frames of reference and associated coordinate conditions. In this paper we use and compare two classes of time-like congruences and corresponding adapted coordinates: the harmonic and quo-harmonic classes. Besides the intrinsic definition and some of their intrinsic properties and differences we consider with some detail their differences at the level of the linearized approximation of the field equations. The hard part of this paper is an explicit and general determination of the harmonic and quo-harmonic coordinates adapted to the stationary character of three well-know metrics, Schwarzschild's, Curzon's and Kerr's, to order five of their asymptotic expansions. It also contains some relevant remarks on such problems as defining the multipoles of vacuum solutions or matching interior and exterior solutions.Comment: 27 pages, no figure

Frame dragging and super-energy

We show that the vorticity appearing in stationary vacuum spacetimes is always related to the existence of a flow of super-energy on the plane orthogonal to the vorticity vector. This result, toghether with the previously established link between vorticity and super--energy in radiative (Bondi-Sachs) spacetimes strength further the case for this latter quantity as the cause of frame dragging.Comment: 12 pages Latex. To appear in Phys.Rev. D. Typos correcte

Energy and Momentum Distributions of a (2+1)-dimensional black hole background

Using Einstein, Landau-Lifshitz, Papapetrou and Weinberg energy-momentum complexes we explicitly evaluate the energy and momentum distributions associated with a non-static and circularly symmetric three-dimensional spacetime. The gravitational background under study is an exact solution of the Einstein's equations in the presence of a cosmological constant and a null fluid. It can be regarded as the three-dimensional analogue of the Vaidya metric and represents a non-static spinless (2+1)-dimensional black hole with an outflux of null radiation. All four above-mentioned prescriptions give exactly the same energy and momentum distributions for the specific black hole background. Therefore, the results obtained here provide evidence in support of the claim that for a given gravitational background, different energy-momentum complexes can give identical results in three dimensions. Furthermore, in the limit of zero cosmological constant the results presented here reproduce the results obtained by Virbhadra who utilized the Landau-Lifshitz energy-momentum complex for the same (2+1)-dimensional black hole background in the absence of a cosmological constant.Comment: 19 pages, LaTeX, v3: references added, to appear in Int.J.Mod.Phys.

Effect of the enzymatic inhibitor of Kunitz on the gastric lesions from reserpine, from phenylbutazone, from pyloric ligation and by restraint in the rat

The protective effects of certain polypeptides on gastric ulcerations caused from reserpine and phenylbutazone in the rate were studied. It was found that the Kunitz enzymatic inhibitor exerts a protective action in regard to gastric lesions. However, the inhibitor did not change the development of Shay ulcers and stress ulcers from restraint

Grid-scale Fluctuations and Forecast Error in Wind Power

The fluctuations in wind power entering an electrical grid (Irish grid) were analyzed and found to exhibit correlated fluctuations with a self-similar structure, a signature of large-scale correlations in atmospheric turbulence. The statistical structure of temporal correlations for fluctuations in generated and forecast time series was used to quantify two types of forecast error: a timescale error ($e_{\tau}$) that quantifies the deviations between the high frequency components of the forecast and the generated time series, and a scaling error ($e_{\zeta}$) that quantifies the degree to which the models fail to predict temporal correlations in the fluctuations of the generated power. With no $a$ $priori$ knowledge of the forecast models, we suggest a simple memory kernel that reduces both the timescale error ($e_{\tau}$) and the scaling error ($e_{\zeta}$)

Bel-Robinson tensor and dominant energy property in the Bianchi type I Universe

Within the framework of Bianchi type-I space-time we study the Bel-Robinson tensor and its impact on the evolution of the Universe. We use different definitions of the Bel-Robinson tensor existing in the literature and compare the results. Finally we investigate the so called "dominant super-energy property" for the Bel-Robinson tensor as a generalization of the usual dominant energy condition for energy momentum tensors. Keywords: Bianchi type I model, super-energy tensors Pacs: 03.65.Pm and 04.20.HaComment: 15 pages, revised version, no figure

Tocar el tango hoy: estilo compositivo y estilo de ejecución

El estilo del tango se ha desarrollado al calor de sus prácticas de ejecución. Para investigarlo se necesita incorporar al análisis de la composición escrita, el estudio de sus rasgos performativos, postulando una interdependencia entre estilo compositivo y estilo de ejecución. Así, movimiento, sonido, texto musical y práctica en contexto forman el corpus del presente trabajo.Área: Ciencias Sociales y Humana

Aproximación a la diferenciación social del espacio interior urbano en la ciudad de Murcia.

Sin resume