Many-body forces in magnetic neutron stars

In this work, we study in detail the effects of many-body forces on the equation of state and the structure of magnetic neutron stars. The stellar matter is described within a relativistic mean field formalism that takes into account many-body forces by means of a non-linear meson field dependence on the nuclear interaction coupling constants. We assume that matter is at zero temperature, charge neutral, in beta-equilibrium, and populated by the baryon octet, electrons, and muons. In order to study the effects of different degrees of stiffness in the equation of state, we explore the parameter space of the model, which reproduces nuclear matter properties at saturation, as well as massive neutron stars. Magnetic field effects are introduced both in the equation of state and in the macroscopic structure of stars by the self-consistent solution of the Einstein-Maxwell equations. In addition, effects of poloidal magnetic fields on the global properties of stars, as well as density and magnetic field profiles are investigated. We find that not only different macroscopic magnetic field distributions, but also different parameterizations of the model for a fixed magnetic field distribution impact the gravitational mass, deformation and internal density profiles of stars. Finally, we also show that strong magnetic fields affect significantly the particle populations of starsComment: accepted by The Astrophysical Journa

Energy and volume of vector fields on spherical domains

We present in this paper a \boundary version" for theorems about minimality of volume and energy functionals on a spherical domain of threedimensional Euclidean sphere

Bond patterns and charge order amplitude in 1/4-filled charge-transfer solids

Metal-insulator transition accompanied by charge-ordering has been widely investigated in quasi-one-dimensional conductors, including in particular organic charge-transfer solids. Among such materials the 1/4-filled band charge-transfer solids are of strong interest, because of the commensurate nature of the charge-ordering in these systems. The period-four charge-order pattern ...1100... here is accompanied by two distinct bond distortion patterns, giving rise to bond-charge-density waves (BCDW) of types 1 and 2. Using quantum Monte Carlo methods, we determine the phase diagram within the extended Hubbard Hamiltonian that gives both types 1 and 2 BCDW in the thermodynamic limit. We further investigate the effect of electron-electron and electron-phonon interactions on the amount of charge disproportionation. Our results show that between these two bond patterns, one (BCDW2) in general coexists with a large magnitude charge order, which is highly sensitive to electron-phonon interactions, while the other (BCDW1) is characterized by weak charge order. We discuss the relevance of our work to experiments on several 1/4-filled conductors, focusing in particular on the materials (EDO-TTF)_2X and (DMEDO-TTF)_2X with large amplitude charge-order.Comment: 7 pages, 8 figure

Manual para elaboração do Plano Municipal de Arborização Urbana.

bitstream/item/96121/1/2013-SergioA-Manual-PMARB.pdfAutores: Alberto Barcellos, Cláudio Renato Wojcikiewicz, Ezimar Andrade Lubaszewski, Jorge Zbigniew Mazuchowski, José Roberto da Conceição, Luciana Leal, Maria Lúcia Miró Medeiros, Paulo Alfonso Conte, Saulo Gomes Karvat, Sérgio Ahrens

The Importance of Asymptotic Freedom for the Pseudocritical Temperature in Magnetized Quark Matter

Although asymptotic freedom is an essential feature of QCD, it is absent in effective chiral quark models like the Nambu--Jona-Lasinio and linear sigma models. In this work we advocate that asymptotic freedom plays a key role in the recently observed discrepancies between results of lattice QCD simulations and quark models regarding the behavior of the pseudocritical temperature $T_{\rm pc}$ for chiral symmetry restoration in the presence of a magnetic field $B$. We show that the lattice predictions that $T_{\rm pc}$ decreases with $B$ can be reproduced within the Nambu--Jona-Lasinio model if the coupling constant $G$ of the model decreases with $B$ and the temperature. Without aiming at numerical precision, we support our claim by considering a simple ansatz for $G$ that mimics the asymptotic freedom behavior of the QCD coupling constant $1/\alpha_s \sim \ln (eB/\Lambda^2_{QCD})$ for large values of $B$.Comment: 5 pages, 4 figures. This version matches the published on