Topological vortices in generalized Born-Infeld-Higgs electrodynamics

A consistent BPS formalism to study the existence of topological axially symmetric vortices in generalized versions of the Born-Infeld-Higgs electrodynamics is implemented. Such a generalization modifies the field dynamics via introduction of three non-negative functions depending only in the Higgs field, namely, $G(|\phi|)$, $w(|\phi|)$ and $V(|\phi|)$. A set of first-order differential equations is attained when these functions satisfy a constraint related to the Ampere law. Such a constraint allows to minimize the system energy in such way that it becomes proportional to the magnetic flux. Our results provides an enhancement of topological vortex solutions in Born-Infeld-Higgs electrodynamics. Finally, we analyze a set of models such that a generalized version of Maxwell-Higgs electrodynamics is recovered in a certain limit of the theory.Comment: 8 pages, 8 figures, to appear in EPJ

Nonsingular charged black holes \`{a} la Palatini

We argue that the quantum nature of matter and gravity should lead to a discretization of the allowed states of the matter confined in the interior of black holes. To support and illustrate this idea, we consider a quadratic extension of General Relativity formulated \`{a} la Palatini and show that nonrotating, electrically charged black holes develop a compact core at the Planck density which is nonsingular if the mass spectrum satisfies a certain discreteness condition. We also find that the area of the core is proportional to the number of charges times the Planck area.Comment: 10 single column page

The optical appearance of a nonsingular de Sitter core black hole geometry under several thin disk emissions

We consider the optical appearance under a thin accretion disk of a regular black hole with a central de Sitter core implementing $\mathcal{O}(l^2/r^2)$ far-corrections to the Schwarzschild black hole. We use the choice $l=0.25M$, which satisfies recently found constraints from the motion of the S2 star around Sgr A$^*$ in this model, and which leads to thermodynamically stable black holes. As the emission model, we suitably adapt ten samples of the Standard Unbound emission profile for a monochromatic intensity in the disk's frame, which have been previously employed in the literature within the context of reproducing General Relativistic Magneto-Hydrodynamic simulations of the accretion flow. We find the usual central brightness depression surrounded by the bright ring cast by the disk's direct emission as well as two non-negligible photon ring contributions. As compared to the usual Schwarzschild solution, the relative luminosities of the latter are significantly boosted, while the size of the former is strongly decreased. We discuss the entanglement of the background geometry and the choice of emission model in generating these black hole images, as well as the capability of these modifications of Schwarzschild solution to pass present and future tests based on their optical appearance when illuminated by an accretion disk.Comment: 12 pages, 5 figure

Where the city lights shine? Measuring the effect of sprawl on electricity consumption in Spain

Urban sprawl is a phenomenon that is generally growing across all continents. As a result, modern city structures need larger areas for similar populations. Few studies have evaluated the effects of sprawl on an important aspect in terms of sustainable development: energy consumption. The aim of this paper is to analyse whether urban sprawl has a significant effect on electricity consumption in Spanish municipalities. The increase in sprawl in Spanish cities is heterogeneous, and the growth of household income during recent decades has allowed households to move to scattered residential areas. This situation makes this country especially interesting as a case study to evaluate the impacts of urban sprawl. In this paper, by disaggregating the electricity consumption of households at the local level using entropy, we measure the effect of sprawl to evaluate whether there is an effect on household energy consumption. The joint consideration of disaggregated data and spatial heterogeneity allows us to assess the effect that sprawl has for certain urban configurations on electricity consumption, which points to the need for policies that involve national, regional and local land use policies

Grindability and combustion behavior of coal and torrefied biomass blends

Biomass samples (pine, black poplar and chestnut woodchips) were torrefied to improve their grindability before being combusted in blends with coal. Torrefaction temperatures between 240 and 300 °C and residence times between 11 and 43 min were studied. The grindability of the torrefied biomass, evaluated from the particle size distribution of the ground sample, significantly improved compared to raw biomass. Higher temperatures increased the proportion of smaller-sized particles after grinding. Torrefied chestnut woodchips (280 °C, 22 min) showed the best grinding properties. This sample was blended with coal (5–55 wt.% biomass). The addition of torrefied biomass to coal up to 15 wt.% did not significantly increase the proportion of large-sized particles after grinding. No relevant differences in the burnout value were detected between the coal and coal/torrefied biomass blends due to the high reactivity of the coal. NO and SO2 emissions decreased as the percentage of torrefied biomass in the blend with coal increased.This work was part of the subcontracted contribution of INCAR to a project carried out by EDP Spain with the financial support from the European Regional Development Fund (ERDF) and acting IDEPA (Economic Development Agency of the Principality of Asturias) as research funding agency (Ref.: IDE/2013/000233). The authors thank A. J. Martín, member of the PrEM group at INCAR-CSIC, for his contribution.Peer reviewe

Thick brane in f(R)f(R) gravity with Palatini dynamics

This work deals with modified gravity in five dimensional spacetime. We study a thick Palatini $f(R)$ brane, that is, a braneworld scenario described by an anti-de Sitter warped geometry with a single extra dimension of infinite extent, sourced by real scalar field under the Palatini approach, where the metric and the connection are regarded as independent degrees of freedom. We consider a first-order framework which we use to provide exact solutions for the scalar field and warp factor. We also investigate a perturbative scenario such that the Palatini approach is implemented through a Lagrangian $f(R)=R+\epsilon R^n$, where the small parameter $\epsilon$ controls the deviation from the standard thick brane case.Comment: 8 double-column pages, 10 figures, revtex4-1 style. Several modificacions added in Sections I, II, III and IV. To appear in Eur. Phys. J.