Schwinger-Dyson equations and the quark-antiquark static potential

In lattice QCD, a confining potential for a static quark-antiquark pair can be computed with the Wilson loop technique. This potential, dominated by a linear potential at moderate distances, is consistent with the confinement with a flux tube, an extended and scalar system also directly observable in lattice QCD. Quantized flux tubes have also been observed in another class of confinement, the magnetic confinement in type II superconductors. On the other hand the solution of Schwinger Dyson Equations, say with the Landau gauge fixing and the truncation of the series of Feynman diagrams, already at the rainbow level for the self energy and at the ladder level for the Bethe Salpeter equation, provides a signal of a possible inverse quartic potential in momentum space derived from one gluon and one ghost exchange, consistent with confinement. Here we address the successes, difficulties and open problems of the matching of these two different perspectives of confinement, the Schwinger-Dyson perspective versus the flux tube perspective.Comment: 12 pages, 18 figures; talk presented at QCD-TNT, Trento, 7-11 sep 200

Gluons at finite temperature

The gluon propagator is investigated at finite temperature via lattice simulations. In particular, we discuss its interpretation as a massive-type bosonic propagator. Moreover, we compute the corresponding spectral density and study the violation of spectral positivity. Finally, we explore the dependence of the gluon propagator on the phase of the Polyakov loop

Sistemas diversificados com olerícolas em áreas de várzea alta do Município de Iranduba-AM.

Realizou-se um inventário formal das práticas e tecnologias em uso por agricultores familiares de municípios circunvizinhos à capital do Estado, Manaus, grande centro demandador de alimentos, e neste trabalho, são descritos sistemas diversificados com olerícolas, detectados em um dos municípios objeto de estudo, em ecossistema de várzea

Problemas fitossanitários e solução tecnológica na produção de cucurbitáceas por agricultores familiares do Estado do Amazonas.

O objetivo deste trabalho foi realizar um levantamento das doenças fúngicas e bacterianas incidentes sobre as cucurbitáceas cultivadas, e comentar as soluçções tecnológicas adotadas pelos agricultores, à luz de práticas agroecológicas. Adicionalmente, foram registrados aspectos relativos a insetos-pragas

The lattice gluon propagator in renormalizable ξ\xi gauges

We study the SU(3) gluon propagator in renormalizable $R_\xi$ gauges implemented on a symmetric lattice with a total volume of (3.25 fm)$^4$ for values of the guage fixing parameter up to $\xi=0.5$. As expected, the longitudinal gluon dressing function stays constant at its tree-level value $\xi$. Similar to the Landau gauge, the transverse $R_\xi$ gauge gluon propagator saturates at a non-vanishing value in the deep infrared for all values of $\xi$ studied. We compare with very recent continuum studies and perform a simple analysis of the found saturation with a dynamically generated effective gluon mass.Comment: 6 pages, 4 figure