Search results for "Modelo"
showing 10 items of 444 documents
Europa y la televisión pública
1997
Cinq facteurs clés pour comprendre les territoires sportifs
2006
Pour expliquer la répartition spatiale des activités sportives et la création de territoires sportifs, cet article envisage cinq facteurs clés qui sont les fondements nécessaires de toute analyse. La répartition de la population introduit un effet de masse sous-jacent à toute pratique d’une activité sportive ; le milieu physique, s’il n’en demeure pas moins indispensable pour comprendre la localisation de certains sports, subit un processus d’artificialisation ; la diffusion spatiale introduit une dimension historique obligatoire ; même contestée, l’influence de l’espace social au sens large se fait ressentir à condition d’utiliser la bonne échelle d’analyse ; enfin, la dynamique spatiale i…
Modelización de la función de covarianza en procesos espacio-temporales : análisis y aplicaciones
2008
Desde sus orígenes durante la segunda mitad del siglo XX hasta la actualidad ha quedado suficientemente demostrada la validez de las técnicas geoestadísticas para el estudio de todo tipo de procesos naturales que se manifiestan sobre localizaciones espaciales. Durante los últimos años del siglo pasado y principios de este se observa en la literatura especializada una creciente demanda de técnicas estadísticas espacio-temporales que generalicen los procedimientos meramente espaciales para fenómenos espaciales de los que se conoce su evolución temporal. Es especialmente reseñable las numerosas aportaciones realizadas por los investigadores para la construcción de funciones de covarianza espac…
Multiring images of thin accretion disk of a regular naked compact object
2022
We discuss the importance of multi-ring images in the optical appearance of a horizonless spherically symmetric compact object, when illuminated by an optically thin accretion disk. Such an object corresponds to a sub-case of an analytically tractable extension of the Kerr solution dubbed as the {\it eye of the storm} by Simpson and Visser in [JCAP \textbf{03} (2022) 011], which merits in removing curvature singularities via an asymptotically Minkowski core, while harbouring both a critical curve and an infinite potential barrier at the center for null geodesics. This multi-ring structure is induced by light rays winding several times around the object, and whose luminosity is significantly…
Minimum main sequence mass in quadratic Palatini f ( R ) gravity
2019
General relativity yields an analytical prediction of a minimum required mass of roughly ∼0.08-0.09 M for a star to stably burn sufficient hydrogen to fully compensate photospheric losses and, therefore, to belong to the main sequence. Those objects below this threshold (brown dwarfs) eventually cool down without any chance to stabilize their internal temperature. In this work we consider quadratic Palatini f(R) gravity and show that the corresponding Newtonian hydrostatic equilibrium equation contains a new term whose effect is to introduce a weakening/strengthening of the gravitational interaction inside astrophysical bodies. This fact modifies the general relativity prediction for this m…
La investigación en el diseño. Un modelo basado en la experiencia
2010
Rodriguez, L. M. (2016). Psicología del desarrollo moral en la adolescencia. Un modelo integrativo. Pontificia Universidad Católica Argentina, Santa …
2018
Light ring images of double photon spheres in black hole and wormhole spacetimes
2022
The silhouette of a black hole having a critical curve (an unstable bound photon orbit) when illuminated by an optically thin accretion disk whose emission is confined to the equatorial plane shows a distinctive central brightness depression (the shadow) whose outer edge consists of a series of strongly lensed, self-similar rings superimposed with the disk's direct emission. While the size and shape of the critical curve depend only on the background geometry, the pattern of bright and dark regions (including the size and depth of the shadow itself) in the image is strongly influenced by the (astro)physics of the accretion disk. This aspect makes it difficult to extract clean and clear obse…
Structure and stability of traversable thin-shell wormholes in Palatini f(R) gravity
2020
We study the structure and stability of traversable wormholes built as (spherically symmetric) thin shells in the context of Palatini f(R) gravity. Using a suitable junction formalism for these theories we find that the effective number of degrees of freedom on the shell is reduced to a single one, which fixes the equation of state to be that of massless stress-energy fields, contrary to the general relativistic and metric f(R) cases. Another major difference is that the surface energy density threading the thin shell, needed in order to sustain the wormhole, can take any sign and may even vanish, depending on the desired features of the corresponding solutions. We illustrate our results by…
Geometric inequivalence of metric and Palatini formulations of General Relativity
2020
Projective invariance is a symmetry of the Palatini version of General Relativity which is not present in the metric formulation. The fact that the Riemann tensor changes nontrivially under projective transformations implies that, unlike in the usual metric approach, in the Palatini formulation this tensor is subject to a gauge freedom, which allows some ambiguities even in its scalar contractions. In this sense, we show that for the Schwarzschild solution there exists a projective gauge in which the (affine) Kretschmann scalar, K≡R R , can be set to vanish everywhere. This puts forward that the divergence of curvature scalars may, in some cases, be avoided by a gauge transformation of the …