4,449 research outputs found
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 () that quantifies the deviations between
the high frequency components of the forecast and the generated time series,
and a scaling error () that quantifies the degree to which the
models fail to predict temporal correlations in the fluctuations of the
generated power. With no knowledge of the forecast models, we
suggest a simple memory kernel that reduces both the timescale error
() and the scaling error ()
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
Aproximación a la diferenciación social del espacio interior urbano en la ciudad de Murcia.
Sin resume
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
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