Solid State Analog for He-McKellar-Wilkens Quantum Phase

In this letter we investigate the quantum dynamics of a quasiparticle in the presence of a charged screw dislocation submitted to a uniform magnetic field. Analysing the quantum scattering for this quasiparticle we observed the appearance of a topological quantum phase in the solution and demonstrate that this phenomenon is the solid state analog of the He-McKeller-Wilkens effect.Comment: 7 pages, epl styl

Bound states in the dynamics of a dipole in the presence of a conical defect

In this work we investigate the quantum dynamics of an electric dipole in a $(2+1)$-dimensional conical spacetime. For specific conditions, the Schr\"odinger equation is solved and bound states are found with the energy spectrum and eigenfunctions determined. We find that the bound states spectrum extends from minus infinity to zero with a point of accumulation at zero. This unphysical result is fixed when a finite radius for the defect is introduced.Comment: 4 page

The self-energy of a charged particle in the presence of a topological defect distribution

In this work we study a charged particle in the presence of both a continuous distribution of disclinations and a continuous distribution of edge dislocations in the framework of the geometrical theory of defects. We obtain the self-energy for a single charge both in the internal and external regions of either distribution. For both distributions the result outside the defect distribution is the self-energy that a single charge experiments in the presence of a single defect.Comment: 12 pages, Revtex4, two figures,to appear in Int. Joun. Mod. Phys.

Electrostatic self-force in (2+1)-dimensional cosmological gravity

Point sources in (2+1)-dimensional gravity are conical singularities that modify the global curvature of the space giving rise to self-interaction effects on classical fields. In this work we study the electrostatic self-interaction of a point charge in the presence of point masses in (2+1)-dimensional gravity with a cosmological constant.Comment: 9 pages, Late

Distribuição das Esponjas (Porifera) na Reserva Biológica do Atol das Rocas, Nordeste do Brasil

Due to the richness and uniqueness of its fauna, Atol das Rocas harbours the first Marine Biological Reserve in Brazil, but only six species of sponges were previously recorded from the atoll. In the present study the structure of the sponge community in the Biological Reserve of Atol das Rocas is described through quali- and quantitative sampling in 18 collection sites. Thirty-six sponge species from 24 families were found, which summed with previous records makes a total of 39 species now known from the atoll. At least six species are new, and four (Plakortis sp.3, Clathrina sp., Holoxea violacea and Aplysina sp.) are provisionally endemic of Atol das Rocas. Total species diversity and evenness were moderately high (H=2.38, J=0.71), as well as total sponge abundance (14.2 ind.m-2). Spirastrella hartmani (5.4 ind.m-2) and Chondrilla aff. nucula (1.1 ind.m-2) were the most abundant sponge species in the atoll. Highest sponge diversity (H’= 2.13) and density (70.4 ind.m-2) were found at Fenda site, a cryptic environment with low water movement and 7m depth. The lowest diversity (H’= 0.22) and density (1.7 ind.m-2) were found at the shallow (10-30cm depth), exposed tide pools. Atol das Rocas shares several sponge species with Fernando de Noronha (13/39) and with the littoral of Pernambuco (12/39). The degree of endemism of the sponge community observed in the atoll was low (10%) if compared to New Caledonia reef for example (71%), but this number can increase with more collections and refinement of taxonomic studies.Devido à riqueza e à unicidade de sua fauna, o Atol das Rocas abriga a primeira Reserva Biológica Marinha do Brasil, mas apenas seis espécies de esponjas foram registradas anteriormente no local. Neste trabalho é descrita a estrutura da comunidade de Porifera da Reserva Biológica do Atol das Rocas, através de amostragens quali- e quantitativas em 18 estações de coleta. Foram encontradas 36 espécies de 24 famílias, que somadas aos registros anteriores perfazem 39 espécies conhecidas no atol. Provavelmente seis destas espécies são novas, e quatro (Plakortis sp.3, Clathrina sp., Holoxea violacea e Aplysina sp.) são provisoriamente endêmicas para o Atol das Rocas. A diversidade e a equitabilidade das espécies de esponjas foi moderadamente alta (H=2,38, J=0,71), assim como a abundância total de esponjas (14,2 ind.m-2). Spirastrella hartmani (5,4 ind.m-2) e Chondrilla aff. nucula (1,1 ind.m-2) são as espécies de Porifera mais abundantes na área. O local com a maior diversidade (H’= 2,2) e densidade (70,4 ind.m-2) de esponjas foi a Fenda, um ambiente críptico com baixo hidrodinamismo e 7m de profundidade. As Poças de Maré, rasas e expostas à luz e às ondas, apresentaram a menor diversidade (H’= 0,22) e densidade de esponjas (1,7 ind.m-2). O Atol das Rocas possui muitas espécies de esponjas em comum com Fernando de Noronha (13/39) e com o litoral pernambucano (12/39). O grau de endemismo de esponjas verificado no Atol das Rocas foi baixo (10%) quando comparado por exemplo com o Recife da Nova Caledônia (71%), mas esse número pode aumentar com mais coletas e o refinamento dos estudos taxonômicos

Loop variables in the geometry of a rotating black string

In this paper we analyze in the Wilson loop context the parallel transport of vectors and spinors around a closed loop in the background space-time of a rotating black string in order to classify its global properties. We also examine particular closed orbits in this space-time and verify the Mandelstam relations.Comment: 14 pages, iopart styl