A Newtonian approach to the cosmological dark fluids

We review the hydrodynamics of the dark sector components in Cosmology. For this purpose we use the approach of Newtonian gravitational instability, and thereafter we add corrections to arrive to a full relativistic description. In Cosmology and Astrophysics, it is usual to decompose the dark sector into two species, dark matter and dark energy. We will use instead a unified approach by describing a single unified dark fluid with very simple assumptions, namely the dark fluid is barotropic and its sound speed vanishes.Comment: 13 pages, To be published in 'Selected Topics of Computational and Experimental Fluid Mechanics' Springer Book Series: Environmental Science and Engineering: Environmental Scienc

Productivity of a \u3cem\u3eLeucaena Leucocephala-Cynodon Nlemfuensis\u3c/em\u3e Silvopastoral System with Sheep in Yucatan, Mexico

Animal production in the tropics of Mexico is based on grazed grasslands of low productivity; this type of production system has reduced the areas of natural vegetation and damaged the ecology (erosion of flora, fauna and soil). Silvopastoral technologies may improve the welfare and economic conditions of the rural population and, consequently, preserve their natural resources. The current work was designed to assess the introduction of Leucaena leucocephala in a silvopastoral system with Cynodon nlemfuensis (star grass) grazed by sheep

Constant mean curvature solutions of the Einstein-scalar field constraint equations on asymptotically hyperbolic manifolds

We follow the approach employed by Y. Choquet-Bruhat, J. Isenberg and D. Pollack in the case of closed manifolds and establish existence and non-existence results for the Einstein-scalar field constraint equations on asymptotically hyperbolic manifolds.Comment: 15 page

Probing two approaches to Unified Dark Dynamics

Dark matter and dark energy are essential in the description of the late Universe, since at least the epoch of equality. On the other hand, the inflation is also necessary and demands a "dark" component, usually associated to a scalar field that dominated the dynamics and kinematics in the very early Universe. Yet, these three dark components of standard model of cosmology are independent from each other, although there are alternative models that pursue to achieve a triple unification, or at least a double. In the present work we present an update of two models that we have considered in recent years. The first is the "dark fluid" model in which dark matter and dark energy are the same thing, achieving a double unification with specific properties that exactly emulate the standard model of cosmology, given the dark degeneracy that exists in the LCDM model. The second model is given by a single F(X) scalar field Lagrangian, with which one is able to model the whole cosmological dynamics, from inflation to today, representing a triple unification model. We highlight the main properties of these models, as well as we test them against known cosmological probes.Comment: 20 pages, 5 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1108.245

The Ricci flow of asymptotically hyperbolic mass and applications

We consider the evolution of the asymptotically hyperbolic mass under the curvature-normalized Ricci flow of asymptotically hyperbolic, conformally compactifiable manifolds. In contrast to asymptotically flat manifolds, for which ADM mass is constant during Ricci flow, we show that the mass of an asymptotically hyperbolic manifold of dimension n>2 decays smoothly to zero exponentially in the flow time. From this, we obtain a no-breathers theorem and a Ricci flow based, modified proof of the scalar curvature rigidity of zero-mass asymptotically hyperbolic manifolds. We argue that the nonconstant time evolution of the asymptotically hyperbolic mass is natural in light of a conjecture of Horowitz and Myers, and is a test of that conjecture. Finally, we use a simple parabolic scaling argument to produce a heuristic "derivation" of the constancy of ADM mass under asymptotically flat Ricci flow, starting from our decay formula for the asymptotically hyperbolic mass under the curvature-normalized flow.Comment: Revised in accord with referee comments, typos and minor errors corrected, Appendix B added, footnotes in-lined; version accepted for publicatio