Addendum: Behavior of a bipartite system in a cavity

This note is an Addendum to our previous article [Phys. Rev. A \textbf{81}, 053820 (2010)]. We show that under the assumption of a Bose-Einstein distribution for the thermal reservoir, zero-temperature properties of the entangled states considered there are not changed by heating, for temperatures up to the order of room temperatures. In this case, the system is dissipative in free space and presents stability for a small cavity, both for T=0 and for finite temperature.Comment: Revtex, 04 pages no figures, Version as accepted for publication in Phys. Rev.

A note on the infrared behavior of the compactified Ginzburg--Landau model in a magnetic field

We consider the Euclidean large-$N$ Ginzburg--Landau model in $D$ dimensions, $d$ ($d\leq D$) of them being compactified. For D=3, the system can be supposed to describe, in the cases of d=1, d=2, and d=3, respectively, a superconducting material in the form of a film, of an infinitely long wire having a rectangular cross-section and of a brick-shaped grain. We investigate the fixed-point structure of the model, in the presence of an external magnetic field. An infrared-stable fixed points is found, which is independent of the number of compactified dimensions. This generalizes previous work for type-II superconducting filmsComment: LATEX, 6 pages no figures. arXiv admin note: 80% of text overlaps with arXiv:1102.139

Magnetic effects on spontaneous symmetry breaking/restoration in a toroidal topology

We study temperature and finite-size effects on the spontaneous symmetry breaking/restoration for a scalar field model under the influence of an external magnetic field, at finite chemical potential. We use the 2PI formalism and consider the large-$N$ limit. We find that there is a minimal size of the system to sustain the broken phase, which diminishes as the applied field increases but is independent of the chemical potential. We analyze the critical curves and show that the magnetic field enhances the broken-phase regions, while increasing the chemical potential leads to a diminishement of the critical temperature.Comment: Five pages, five figures, version as accepted for publication in Phys. Rev.

Behavior of a bipartite system in a cavity

We study the time evolution of a superposition of product states of two dressed atoms in a spherical cavity in the situations of an arbitrarily large cavity (free space) and of a small one. In the large-cavity case, the system dissipates, whereas, for the small cavity, the system evolves in an oscillating way and never completely decays. We verify that the von Neumann entropy for such a system does not depend on time, nor on the size of the cavityComment: 9 pages 2 figures, Revtex, Version accepted to be published in Physical Review

An analysis of landscape fragmentation in the Brazilian Amazon based on deforestation data derived from Landsat imagery.

Deforestation in the Brazilian Amazon has produced fragmentation of the largest tropical rain forest in the planet resulting in impacts over biodiversity and the functioning of ecosystems. Most of the deforestation is known to be concentrated near major roads and areas of pioneer colonization, but few studies have quantitatively analyzed patterns and processes of landscape fragmentation associated with this spatial dynamics. In this paper we evaluate the effect of forest clearing based on two landscape metrics - percent cleared and percolation - for areas in the states of Mato Grosso, Pará, and Rondônia where the largest rates of deforestation have been observed. Deforestation data included one data set derived from Landsat MSS imagery for the 1970?s and one based on Landsat TM imagery for 2006. Forest fragments in 2006 within 25-km of areas deforested since 1978 - where a large majority of recent deforestation has been concentrated - were analyzed to assess how landscape fragmentation has evolved following the diffusion of forest clearing within a relatively close neighborhood of the 1978 deforestation. The distribution of deforestation for regular ¼-degree grid cells with different values of percent cleared was estimated as a proxy for the distribution of the equivalent metric based on actual farm limits. The fractions of deforestation for larger categories of percent cleared have increased during the diffusion of forest clearing and a majority of the total 2006 deforestation belonged to areas with less than 50% of forest remnants, taking as reference the Brazilian forest regulations. The diffusion of deforestation has resulted in different patterns of landscape fragmentation based on estimated percolation and we propose an analysis of such patterns based on geographic differences