Local Physical Coodinates from Symplectic Projector Method

The basic arguments underlying the symplectic projector method are presented. By this method, local free coordinates on the constrait surface can be obtained for a broader class of constrained systems. Some interesting examples are analyzed.Comment: 8 page

Entropic Law of Force, Emergent Gravity and the Uncertainty Principle

The entropic formulation of the inertia and the gravity relies on quantum, geometrical and informational arguments. The fact that the results are completly classical is missleading. In this paper we argue that the entropic formulation provides new insights into the quantum nature of the inertia and the gravity. We use the entropic postulate to determine the quantum uncertainty in the law of inertia and in the law of gravity in the Newtonian Mechanics, the Special Relativity and in the General Relativity. These results are obtained by considering the most general quantum property of the matter represented by the Uncertainty Principle and by postulating an expression for the uncertainty of the entropy such that: i) it is the simplest quantum generalization of the postulate of the variation of the entropy and ii) it reduces to the variation of the entropy in the absence of the uncertainty.Comment: 10 pages. Important discussion of the special relativistic case and the newtonian limit of the general relativistic case added. The paper has been reformatted. The authorship listing corrected. (It has been published by mistake out of order in the first version. We have been adhering to the Hardy-Littlewood Rule over the years.) Typos corrected. Four references adde

DSMC evaluation of the Navier-Stokes shear viscosity of a granular fluid

A method based on the simple shear flow modified by the introduction of a deterministic non-conservative force and a stochastic process is proposed to measure the Navier-Stokes shear viscosity in a granular fluid described by the Enskog equation. The method is implemented in DSMC simulations for a wide range of values of dissipation and density. It is observed that, after a certain transient period, the system reaches a hydrodynamic stage which tends to the Navier-Stokes regime for long times. The results are compared with theoretical predictions obtained from the Chapman-Enskog method in the leading Sonine approximation, showing quite a good agreement, even for strong dissipation.Comment: 6 pages, 4 figures; to appear in Rarefied Gas Dynamics: 24th International Symposium (AIP Conference Proceedings

The Contribution of the First Stars to the Cosmic Infrared Background

We calculate the contribution to the cosmic infrared background from very massive metal-free stars at high redshift. We explore two plausible star-formation models and two limiting cases for the reprocessing of the ionizing stellar emission. We find that Population III stars may contribute significantly to the cosmic near-infrared background if the following conditions are met: (i) The first stars were massive, with M > ~100 M_sun. (ii) Molecular hydrogen can cool baryons in low-mass haloes. (iii) Pop III star formation is ongoing, and not shut off through negative feedback effects. (iv) Virialized haloes form stars at about 40 per cent efficiency up to the redshift of reionization, z~7. (v) The escape fraction of the ionizing radiation into the intergalactic medium is small. (vi) Nearly all of the stars end up in massive black holes without contributing to the metal enrichment of the Universe.Comment: 11 pages, 6 figures, expanded discussion, added mid-IR to Fig 6, MNRAS in pres

Exclusive photoproduction of quarkonium in proton-nucleus collisions at energies available at the CERN Large Hadron Collider

In this work we investigate the coherent photoproduction of psi(1S), psi(2S) and Upsilon (1S) states in the proton-nucleus collisions in the LHC energies. Predictions for the rapidity distributions are presented using the color dipole formalism and including saturation effects that are expected to be relevant at high energies. Calculations are done at the energy 5.02 TeV and also for the next LHC run at 8.8 TeV in proton-lead mode. Discussion is performed on the main theoretical uncertainties associated to the calculations.Comment: 05 pages, 5 figures. Version to be published in Phys. Rev.