Time filter

Source Type

Chaur M.N.,University of Santiago de Cali
Acta Crystallographica Section E: Structure Reports Online | Year: 2013

In the mononuclear title complex, [ZnCl2(C15H16N4O)], the ZnII cation is five-coordinated in a strongly distorted square-pyramidal environment by two Cl- anions and a neutral tridentate Schiff base ligand. The ZnII cation is chelated by the carbonyl O atom, the imine N atom and the pyridine N atom, which causes a slight loss of planarity for the ligand; the dihedral angle between the aromatic rings is 4.61 (8)°.

Moreno-Fuquen R.,University of Santiago de Cali
Acta Crystallographica Section E: Structure Reports Online | Year: 2013

In the title benzoate derivative, C13H6BrN 3O8, the benzene rings form a dihedral angle of 80.90 (9)°. The ester moiety forms dihedral angles of 3.2 (2) and 82.8 4(10)° with the benzene and picryl rings, respectively. The Br atom is disordered over two positions, with the site occupancy for the minor component being 0.48 (4). The crystal structure features C-H⋯O interactions, which generate a three-dimensional network.

Bueno Sanchez J.C.,University of Santiago de Cali | Bueno Sanchez J.C.,Antonio Narino University | Bueno Sanchez J.C.,Industrial University of Santander | Bueno Sanchez J.C.,Complutense University of Madrid
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Single-field inflation, arguably the simplest and most compelling paradigm for the origin of our Universe, is strongly supported by the recent results of the Planck satellite and the BICEP2 experiment. The results from Planck, however, also confirm the presence of a number of anomalies in the Cosmic Microwave Background (CMB), whose origin becomes problematic in single-field inflation. Among the most prominent and well-tested of these anomalies is the Cold Spot, which constitutes the only significant deviation from Gaussianity in the CMB. Planck's non-detection of primordial non-Gaussianity on smaller scales thus suggests the existence of a physical mechanism whereby significant non-Gaussianity is generated on large angular scales only. In this Letter, we address this question by developing a localized version of the inhomogeneous reheating scenario, which postulates the existence of a scalar field able to modify the decay of the inflaton on localized spatial regions only. We demonstrate that if the Cold Spot is due to an overdensity in the last scattering surface, the localization mechanism offers a feasible explanation for it, thus providing a physical mechanism for the generation of localized non-Gaussianity in the CMB. If, on the contrary, the Cold Spot is caused by a newly discovered supervoid (as recently claimed), we argue that the localization mechanism, while managing to enhance underdensities, may well shed light on the rarity of the discovered supervoid. © 2014 The Author.

Pachon L.A.,University of Antioquia | Rueda J.A.,University of Rome La Sapienza | Valenzuela-Toledo C.A.,University of Santiago de Cali
Astrophysical Journal | Year: 2012

Whether or not analytic exact vacuum (electrovacuum) solutions of the Einstein (Einstein-Maxwell) field equations can accurately describe the exterior space-time of compact stars still remains an interesting open question in relativistic astrophysics. As an attempt to establish their level of accuracy, the radii of the innermost stable circular orbits (ISCOs) of test particles given by analytic exterior space-time geometries have been compared with those given by numerical solutions for neutron stars (NSs) obeying a realistic equation of state (EOS). It has been so shown that the six-parametric solution of Pachón et al. (PRS) more accurately describes the NS ISCO radii than other analytic models do. We propose here an additional test of accuracy for analytic exterior geometries based on the comparison of orbital frequencies of neutral test particles. We compute the Keplerian, frame-dragging, and precession and oscillation frequencies of the radial and vertical motions of neutral test particles for the Kerr and PRS geometries and then compare them with the numerical values obtained by Morsink & Stella for realistic NSs. We identify the role of high-order multipole moments such as the mass quadrupole and current octupole in the determination of the orbital frequencies, especially in the rapid rotation regime. The results of this work are relevant to cast a separatrix between black hole and NS signatures and to probe the nuclear-matter EOS and NS parameters from the quasi-periodic oscillations observed in low-mass X-ray binaries. © 2012. The American Astronomical Society. All rights reserved.

Miranda O.G.,CINVESTAV | Moura C.A.,Federal University of ABC | Parada A.,CINVESTAV | Parada A.,University of Santiago de Cali
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

Interest in light dark matter candidates has recently increased in the literature; some of these works consider the role of additional neutrinos, either active or sterile. Furthermore, extragalactic neutrinos have been detected with energies higher than have ever been reported before. This opens a new window of opportunities to the study of neutrino properties that were unreachable up to now. We investigate how an interaction potential between neutrinos and dark matter might induce a resonant enhancement in the oscillation probability, an effect that may be tested with future neutrino data. © 2015 The Authors.

Discover hidden collaborations