16,543 research outputs found
The complex Sine-Gordon equation as a symmetry flow of the AKNS Hierarchy
It is shown how the complex sine-Gordon equation arises as a symmetry flow of
the AKNS hierarchy. The AKNS hierarchy is extended by the ``negative'' symmetry
flows forming the Borel loop algebra. The complex sine-Gordon and the vector
Nonlinear Schrodinger equations appear as lowest negative and second positive
flows within the extended hierarchy. This is fully analogous to the well-known
connection between the sine-Gordon and mKdV equations within the extended mKdV
hierarchy.
A general formalism for a Toda-like symmetry occupying the ``negative''
sector of sl(N) constrained KP hierarchy and giving rise to the negative Borel
sl(N) loop algebra is indicated.Comment: 8 pages, LaTeX, typos corrected, references update
Supersymmetry for integrable hierarchies on loop superalgebras
The algebraic approach is employed to formulate N=2 supersymmetry
transformations in the context of integrable systems based on loop
superalgebras with homogeneous gradation. We
work with extended integrable hierarchies, which contain supersymmetric AKNS
and Lund-Regge sectors.
We derive the one-soliton solution for which solves positive and
negative evolution equations of the N=2 supersymmetric model.Comment: Latex, 21 page
Nontrivial temporal scaling in a Galilean stick-slip dynamics
We examine the stick-slip fluctuating response of a rough massive
non-rotating cylinder moving on a rough inclined groove which is submitted to
weak external perturbations and which is maintained well below the angle of
repose. The experiments presented here, which are reminiscent of the Galileo's
works with rolling objects on inclines, have brought in the last years
important new insights into the friction between surfaces in relative motion
and are of relevance for earthquakes, differing from classical block-spring
models by the mechanism of energy input in the system. Robust nontrivial
temporal scaling laws appearing in the dynamics of this system are reported,
and it is shown that the time-support where dissipation occurs approaches a
statistical fractal set with a fixed value of dimension. The distribution of
periods of inactivity in the intermittent motion of the cylinder is also
studied and found to be closely related to the lacunarity of a random version
of the classic triadic Cantor set on the line.Comment: 7 pages including 6 figure
Orbit determination of Transneptunian objects and Centaurs for the prediction of stellar occultations
The prediction of stellar occultations by Transneptunian objects and Centaurs
is a difficult challenge that requires accuracy both in the occulted star
position as for the object ephemeris. Until now, the most used method of
prediction involving tens of TNOs/Centaurs was to consider a constant offset
for the right ascension and for the declination with respect to a reference
ephemeris. This offset is determined as the difference between the most recent
observations of the TNO and the reference ephemeris. This method can be
successfully applied when the offset remains constant with time. This paper
presents an alternative method of prediction based on a new accurate orbit
determination procedure, which uses all the available positions of the TNO from
the Minor Planet Center database plus sets of new astrometric positions from
unpublished observations. The orbit determination is performed through a
numerical integration procedure (NIMA), in which we develop a specific
weighting scheme. The NIMA method was applied for 51 selected TNOs/Centaurs.
For this purpose, we have performed about 2900 new observations during
2007-2014. Using NIMA, we succeed in predicting the stellar occultations of 10
TNOs and 3 Centaurs between 2013 and 2015. By comparing the NIMA and JPL
ephemerides, we highlighted the variation of the offset between them with time.
Giving examples, we show that the constant offset method could not accurately
predict 6 out of the 13 observed positive occultations successfully predicted
by NIMA. The results indicate that NIMA is capable of efficiently refine the
orbits of these bodies. Finally, we show that the astrometric positions given
by positive occultations can help to further refine the orbit of the TNO and
consequently the future predictions. We also provide the unpublished
observations of the 51 selected TNOs and their ephemeris in a usable format by
the SPICE library.Comment: 12 pages, 9 figures, accepted in A&
Cooperative localization-delocalization in the high Tc cuprates
The intrinsic metastable crystal structure of the cuprates results in local
dynamical lattice instabilities, strongly coupled to the density fluctuations
of the charge carriers. They acquire in this way simultaneously both,
delocalized and localized features. It is responsible for a partial fractioning
of the Fermi surface, i.e., the Fermi surface gets hidden in a region around
the anti-nodal points, because of the opening of a pseudogap in the normal
state, arising from a partial charge localization. The high energy localized
single-particle features are a result of a segregation of the homogeneous
crystal structure into checker-board local nano-size structures, which breaks
the local translational and rotational symmetry. The pairing in such a system
is dynamical rather than static, whereby charge carriers get momentarily
trapped into pairs in a deformable dynamically fluctuating ligand environment.
We conclude that the intrinsically heterogeneous structure of the cuprates must
play an important role in this type of superconductivity.Comment: 14 pages, 8 figures, Proceedings of the "International Conference on
Condensed Matter Theories", Quito, 2009 Int. J. Mod. Phys. B 2010 (Accepted
Exigência de fósforo disponível para frangos de corte nas fases de crescimento e terminação.
bitstream/item/58575/1/CUsersPiazzonDocuments211.pd
Radiative Corrections to the Aharonov-Bohm Scattering
We consider the scattering of relativistic electrons from a thin magnetic
flux tube and perturbatively calculate the order , radiative
correction, to the first order Born approximation. We show also that the second
order Born amplitude vanishes, and obtain a finite inclusive cross section for
the one-body scattering which incorporates soft photon bremsstrahlung effects.
Moreover, we determine the radiatively corrected Aharonov-Bohm potential and,
in particular, verify that an induced magnetic field is generated outside of
the flux tube.Comment: 14 pages, revtex, 3 figure
Quebra de dormência de sementes de pequi (Caryocar coriaceum Wittm.).
O fruto do pequizeiro possui grande aceitação na culinária regional, sendo consumido com arroz, frango, feijão, podendo ser usado também na fabricação de licor, sorvetes e picolés (VERA, 2004). Contudo, sua exploração ocorre de forma totalmente extrativista (OLIVEIRA, 2009), tornando esta atividade de grande importância socioeconômica, gerando renda e emprego à população do cerrado. O objetivo deste trabalho foi avaliar tratamentos de quebra de dormência de sementes de pequi
Reação de cultivares e clones de batata a Meloidogyne javanica. reaction of potato cultivars and clones to Meloidogyne javanica.
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