The Role of Fermions in Bubble Nucleation

We present a study of the role of fermions in the decay of metastable states of a scalar field via bubble nucleation. We analyze both one and three-dimensional systems by using a gradient expansion for the calculation of the fermionic determinant. The results of the one-dimensional case are compared to the exact results of previous work.Comment: 15 pages, revtex, 9 figure

Morphology of low-redshift compact galaxy clusters I. Shapes and radial profiles

The morphology of clusters of galaxies may be described with a set of parameters which contain information about the formation and evolutionary history of these systems. In this paper we present a preliminary study of the morphological parameters of a sample of 28 compact Abell clusters extracted from DPOSS data. The morphology of galaxy clusters is parameterized by their apparent ellipticity, position angle of the major axis, centre coordinates, core radius and beta-model power law index. Our procedure provides estimates of these parameters by simultaneously fitting them all, overcoming some of the difficulties induced by sparse data and low number statistics typical of this kind of analysis. The cluster parameters were fitted in a 3 x 3 h^-2 sqMpc region, measuring the background in a 2 <R< 2.5 h^-1Mpc annulus. We also explore the correlations between shape and profile parameters and other cluster properties. One third of this compact cluster sample has core radii smaller than 50 h^-1 kpc, i.e. near the limit that our data allow us to resolve, possibly consistent with cusped models. The remaining clusters span a broad range of core radii up to 750 h^-1 kpc. More than 80 per cent of this sample has ellipticity higher than 0.2. The alignment between the cluster and the major axis of the dominant galaxy is confirmed, while no correlation is observed with other bright cluster members. No significant correlation is found between cluster richness and ellipticity. Instead, cluster richness is found to correlate, albeit with large scatter, with the cluster core radius.[abridged]Comment: 23 pages, 17 figures, accepted for publication in MNRAS. Full paper including full resolution figures 2 and 9 at http://www.eso.org/~vstrazzu/P/ME1030fv.pd

Ferramenta para integração de dados de recursos naturais dos biomas brasileiros.

O projeto NATDATA, sigla para Plataforma de Integração de Dados dos Recursos Naturais (MACÁRIO et al., 2011) tem como um de seus objetivos criar uma interface para o usuário final das informações sobre os recursos naturais dos biomas brasileiros, ajudando-o com um ambiente intuitivo que permita a consulta rápida e integrada a esses dados. Essa consulta permitirá que haja uma melhor orientação dos investimentos, como uma visão antecipada dos possíveis problemas que alguma região possa sofrer. Devido ao modo heterogêneo com que diversas instituições brasileiras colheram essas informações, há uma grande dificuldade em reaproveitá-las em conjunto. Com isso, o projeto NATDATA foca centralizar essa informação, tornando-a utilizável

Asymptotic analysis of a clamped thin multidomain allowing for fractures and discontinuities

We consider a thin multidomain of $\mathbb R^3,$ consisting of a vertical rod upon a horizontal disk. The equilibrium configurations of the thin hyperelastic multidomain, allowing for fracture and damage, are described by means of a bulk energy density of the kind $W(\nabla U)$, where $W$ is a Borel function with linear growth and $\nabla U$ denotes the gradient of the displacement, i.e. a vector valued function $U:\Omega \to \mathbb R^3$. By assuming that the two volumes tend to zero, under suitable boundary conditions and loads, and suitable assumptions of the rate of convergence of the two volumes, we prove that the limit model is well posed in the union of the limit domains, with dimensions, respectively, $1$ and $2$.Comment: 32 pages, 1 figur

Correlations around an interface

We compute one-loop correlation functions for the fluctuations of an interface using a field theory model. We obtain them from Feynman diagrams drawn with a propagator which is the inverse of the Hamiltonian of a Poschl-Teller problem. We derive an expression for the propagator in terms of elementary functions, show that it corresponds to the usual spectral sum, and use it to calculate quantities such as the surface tension and interface profile in two and three spatial dimensions. The three-dimensional quantities are rederived in a simple, unified manner, whereas those in two dimensions extend the existing literature, and are applicable to thin films. In addition, we compute the one-loop self-energy, which may be extracted from experiment, or from Monte Carlo simulations. Our results may be applied in various scenarios, which include fluctuations around topological defects in cosmology, supersymmetric domain walls, Z(N) bubbles in QCD, domain walls in magnetic systems, interfaces separating Bose-Einstein condensates, and interfaces in binary liquid mixtures.Comment: RevTeX, 13 pages, 6 figure