Static plane symmetric relativistic fluids and empty repelling singular boundaries

We present a detailed analysis of the general exact solution of Einstein's equation corresponding to a static and plane symmetric distribution of matter with density proportional to pressure. We study the geodesics in it and we show that this simple spacetime exhibits very curious properties. In particular, it has a free of matter repelling singular boundary and all geodesics bounce off it.Comment: 9 pages, 1 figure, accepted for publication in Classical and Quantum Gravit

An alternative well-posedness property and static spacetimes with naked singularities

In the first part of this paper, we show that the Cauchy problem for wave propagation in some static spacetimes presenting a singular time-like boundary is well posed, if we only demand the waves to have finite energy, although no boundary condition is required. This feature does not come from essential self-adjointness, which is false in these cases, but from a different phenomenon that we call the alternative well-posedness property, whose origin is due to the degeneracy of the metric components near the boundary. Beyond these examples, in the second part, we characterize the type of degeneracy which leads to this phenomenon.Comment: 34 pages, 3 figures. Accepted for publication in Class. Quantum Gra

On gauge invariant regularization of fermion currents

We compare Schwinger and complex powers methods to construct regularized fermion currents. We show that although both of them are gauge invariant they not always yield the same result.Comment: 10 pages, 1 figur

Duality and bosonization in Schwinger-Keldysh formulation

We present a path-integral bosonization approach for systems out of equilibrium based on a duality transformation of the original Dirac fermion theory combined with the Schwinger-Keldysh time closed contour technique, to handle the non-equilibrium situation. The duality approach to bosonization that we present is valid for $D \geq 2$ space-time dimensions leading for $D=2$ to exact results. In this last case we present the bosonization rules for fermion currents, calculate current-current correlation functions and establish the connection between the fermionic and bosonic distribution functions in a generic, nonequilibrium situation.Comment: 16 pages, 1 figur

Dirac Operator on a disk with global boundary conditions

We compute the functional determinant for a Dirac operator in the presence of an Abelian gauge field on a bidimensional disk, under global boundary conditions of the type introduced by Atiyah-Patodi-Singer. We also discuss the connection between our result and the index theorem.Comment: RevTeX, 11 pages. References adde

Exotic galilean symmetry and the Hall effect

The ``Laughlin'' picture of the Fractional Quantum Hall effect can be derived using the ``exotic'' model based on the two-fold centrally-extended planar Galilei group. When coupled to a planar magnetic field of critical strength determined by the extension parameters, the system becomes singular, and ``Faddeev-Jackiw'' reduction yields the ``Chern-Simons'' mechanics of Dunne, Jackiw, and Trugenberger. The reduced system moves according to the Hall law.Comment: Talk given by P. A. Horvathy at the Joint APCTP- Nankai Symposium. Tianjin (China), Oct.2001. To appear in the Proceedings, to be published by Int. Journ. Mod. Phys. B. 7 pages, LaTex, IJMPB format. no figure

Behavioral Differences Between Two Recently Sympatric Paper Wasps, the Native \u3ci\u3ePolistes Fuscatus\u3c/i\u3e and the Invasive \u3ci\u3ePolistes Dominulus\u3c/i\u3e

Polistes dominulus (Christ), an old world paper wasp, was introduced into the eastern United States in the 1970s and has been rapidly spreading westward. Recently, it has displaced the native Polistes fuscatus (F.) in at least some areas of Michigan. In order to understand why P. dominulus has been so successful, several behavioral attributes were compared between P. dominulus and P. fuscatus at a Michigan field site that contained colonies of both species nest- ing semi-naturally in plywood nestboxes. Preworker colonies of P. dominulus had a significantly greater tendency to store nectar (and had significantly higher proportions of cells with nectar) than preworker colonies of P. fuscatus. This finding may explain the higher survivorship of P. dominulus foundresses reported in a previous study. P. dominulus also had a significantly greater tendency to build vertical nests and had significantly more pedicels per comb and per cell than P. fuscatus. These findings suggest that compared to P. fuscatus, P. dominulus may have more flexibility in the positioning of its combs and, because of a possibly stronger attachment of the comb to a substrate, may be less susceptible to bird predation. The higher winter survivorship reported for P. fuscatus over P. dominulus in a previous study does not appear to be due to differences in the proportions of gynes stranded on their nests late in the fall. Finally, behavioral evidence from videography was consistent with previous reports that P. dominulus is not replacing P. fuscatus through direct agonistic interactions