Towards Noncommutative Linking Numbers Via the Seiberg-Witten Map

In the present work some geometric and topological implications of noncommutative Wilson loops are explored via the Seiberg-Witten map. In the abelian Chern-Simons theory on a three dimensional manifold, it is shown that the effect of noncommutativity is the appearance of $6^n$ new knots at the $n$-th order of the Seiberg-Witten expansion. These knots are trivial homology cycles which are Poincar\'e dual to the high-order Seiberg-Witten potentials. Moreover the linking number of a standard 1-cycle with the Poincar\'e dual of the gauge field is shown to be written as an expansion of the linking number of this 1-cycle with the Poincar\'e dual of the Seiberg-Witten gauge fields. In the process we explicitly compute the noncommutative 'Jones-Witten' invariants up to first order in the noncommutative parameter. Finally in order to exhibit a physical example, we apply these ideas explicitly to the Aharonov-Bohm effect. It is explicitly displayed at first order in the noncommutative parameter, we also show the relation to the noncommutative Landau levels.Comment: 19 pages, 1 figur

An exterior for the G\"{o}del spacetime

We match the vacuum, stationary, cylindrically symmetric solution of Einstein's field equations with $\Lambda$, in a form recently given by Santos, as an exterior to an infinite cylinder of dust cut out of a G\"{o}del universe. There are three cases, depending on the radius of the cylinder. Closed timelike curves are present in the exteriors of some of the solutions. There is a considerable similarity between the spacetimes investigated here and those of van Stockum referring to an infinite cylinder of rotating dust matched to vacuum, with $\Lambda=0$.Comment: 11 pages, LaTeX 2.09, no figures. Submitted to Classical and Quantum Gravit

Arthur Bispo do Rosário: nas tramas da loucura, teceu sua Arte

Este artigo nos remete às reflexões sobre a linha imaginária que possa haver entre a arte e loucura. Com base em que critérios, podemos afirmar que as psicoses se manifestam em arstas pláscos? Ou até que ponto as obras de um psicótico, tais como Arthur Bispo do Rosário, podem ser consideradas obras de arte. Neste contexto, é oportuno questionar: será que a loucura manifesta a arte ou a arte manifesta a loucura? Arthur Bispo do Rosário viveu a maior parte de sua vida na Colônia Juliano Moreira, do Rio de janeiro. Foi submetida às práticas médicas de tratamento padrão, para a época, praticada em pacientes internados. Não obstante, como um cavaleiro solitário, conforme descreve Luciana Hidalgo, criou seu mundo onírico e obedecia às vozes que escutava dentro de si. A partir daí, ia desfiando os tecidos dos uniformes e recolhendo objetos descartados ou em desuso, metamorfoseando-os em obras, hoje consideradas obras de arte, nacional e internacionalmenteABSTRACT: This article regards to the reflecons on the imaginary line that can exist between art and madness. Based on what criteria can we see that the psychoses are manifested in artists? Or to what extent the work of a psychoc, such as Arthur Bispo do Rosário, can be considered works of art? In this context, it is appropriate to ask: will the madness manifests art or art expresses the madness? Arthur Bispo do Rosário lived most of his life in the Juliano Moreira Colony of Rio de Janeiro. He was submied to current medical treatment for the time, practiced in hospitalized patients. Nevertheless, as a lonely rider, as described by Luciana Hidalgo, created his dream world and obeyed the voices inside his head. Thereatier, he unraveled the tissue of uniforms and collected discarded or unused objects, morphing them into pieces now considered works of art, nationally and internationallyinfo:eu-repo/semantics/publishedVersio

Comparison of Monomethylhydrazine/Hydroxypropylcellulose and Hydrocarbon/Silica Gels

Experimental studies have been performed to investigate rheology and droplet burning with different types of gelled propellants. Monomethylhydrazine has been gelled with organic hydroxypropylcellulose. JP-8 and RP-1 hydrocarbon gels have been produced with inorganic fumed silica particles. Rheological characterization showed the differences in terms of viscosity and yield stress behavior due to different types of gelling agents. Herschel-Bulkley and Carreau-Yasuda models have been used to characterize the gels with inorganic and organic gelling agents, respectively. First experiments with the Monomethylhydrazine/hydroxypropylcellulose gels showed a typical swelling process during combustion with a flexible viscous droplet surface. Contrary to that, the hydrocarbon/silica gels burned while a rigid silica structure was built, which remained unburned. Burning drop measurements have been compared to the d^2-squared law

Kerr Geodesics, the Penrose Process and Jet Collimation by a Black Hole

We re-examine the possibility that astrophysical jet collimation may arise from the geometry of rotating black holes and the presence of high-energy particles resulting from a Penrose process, without the help of magnetic fields. Our analysis uses the Weyl coordinates, which are revealed better adapted to the desired shape of the jets. We numerically integrate the 2D-geodesics equations. We give a detailed study of these geodesics and give several numerical examples. Among them are a set of perfectly collimated geodesics with asymptotes $\rho =\rho_{1}$ parallel to the $z-$ axis, with $\rho_{1}$ only depending on the ratios $\frac{\mathcal{Q}}{E^{2}-1}$ and $\frac{a}{M}$, where $a$ and $M$ are the parameters of the Kerr black hole, $E$ the particle energy and $\mathcal{Q}$ the Carter's constant.Comment: Accepted by Astronomy and Astrophysics. AA style with 3 EPS figures. Content amended after AA's refereeing. Discussion of geodesics also corrected and expanded earlier. Conclusions amended accordingl

Instabilities and the roton spectrum of a quasi-1D Bose-Einstein condensed gas with dipole-dipole interactions

We point out the possibility of having a roton-type excitation spectrum in a quasi-1D Bose-Einstein condensate with dipole-dipole interactions. Normally such a system is quite unstable due to the attractive portion of the dipolar interaction. However, by reversing the sign of the dipolar interaction using either a rotating magnetic field or a laser with circular polarization, a stable cigar-shaped configuration can be achieved whose spectrum contains a `roton' minimum analogous to that found in helium II. Dipolar gases also offer the exciting prospect to tune the depth of this `roton' minimum by directly controlling the interparticle interaction strength. When the minimum touches the zero-energy axis the system is once again unstable, possibly to the formation of a density wave.Comment: 7 pages, 6 figures. Special Issue: "Ultracold Polar Molecules: Formation and Collisions