Bifurcations in the theory of current transfer to cathodes of dc discharges and observations of transitions between different modes

General scenarios of transitions between different spot patterns on electrodes of dc gas discharges and their relation to bifurcations of steady-state solutions are analyzed. In the case of cathodes of arc discharges, it is shown that any transition between different modes of current transfer is related to a bifurcation of steady-state solutions. In particular, transitions between diffuse and spot modes on axially symmetric cathodes, frequently observed in the experiment, represent an indication of the presence of pitchfork or fold bifurcations of steady-state solutions. Experimental observations of transitions on cathodes of dc glow microdischarges are analyzed and those potentially related to bifurcations of steady-state solutions are identified. The relevant bifurcations are investigated numerically and the computed patterns are found to conform to those observed in the course of the corresponding transitions in the experiment

Metodologia de extração automática para análise da atualização da rede de drenagem do Estado do Mato Grosso do Sul.

O objetivo deste trabalho foi testar uma metodologia de extração automática da rede de drenagem e comparar os resultados aos mapas gerados de forma manual. O estudo foi realizado nos limites da carta topográfica de Camapuã (SE-21-Z-D, escala 1:250.000), no Estado do Mato Grosso do Sul. Parte da carta abrange o planalto da bacia do Rio Taquari (porção leste) e outra parte abrange a planície do Pantanal (porção oeste), com elevações mais baixas e homogêneas

Gauge fields in a string-cigar braneworld

In this work we investigate the properties of an Abelian gauge vector field in a thin and in a smoothed string-like braneworld, the so-called string-cigar model. This thick brane scenario satisfies the regularity conditions and it can be regarded as an interior and exterior string-like solution. The source undergoes a geometric Ricci flow which is connected to a variation of the bulk cosmological constant. The Ricci flow changes the width and amplitude of the massless mode at the brane core and recover the usual thin string-like behavior at large distances. By numerical means we obtain the Kaluza-Klein (KK) spectrum for both the thin brane and the string-cigar. It turns out that both models exhibit a mass gap between the massless and the massive modes and between the high and the low mass regimes. The KK modes are smooth near the brane and their amplitude are enhanced by the string-cigar core. The analogue Schr\"odinger potential is also tuned by the geometric flow.Comment: The discussion about the Kaluza-Klein spectrum of the gauge field was improved. Numerical analysis was adapted to the conventional notation on Kaluza-Klein number. Some graphics were modified for considering other notation. Results unchanged. References added. Corrected typos. 17 pages. 6 figures. To match version to appears in Physics Letters

Non-Chern-Simons Topological Mass Generation in (2+1) Dimensions

By dimensional reduction of a massive BF theory, a new topological field theory is constructed in (2+1) dimensions. Two different topological terms, one involving a scalar and a Kalb-Ramond fields and another one equivalent to the four-dimensional BF term, are present. We constructed two actions with these topological terms and show that a topological mass generation mechanism can be implemented. Using the non-Chern-Simons topological term, an action is proposed leading to a classical duality relation between Klein-Gordon and Maxwell actions. We also have shown that an action in (2+1) dimensions with the Kalb-Ramond field is related by Buscher's duality transformation to a massive gauge-invariant Stuckelberg-type theory.Comment: 8 pages, no figures, RevTE