439 research outputs found
Condensation of Vortex-Strings: Effective Potential Contribution Through Dual Actions
Topological excitations are believed to play an important role in different
areas of physics. For example, one case of topical interest is the use of dual
models of quantum cromodynamics to understand properties of its vacuum and
confinement through the condensation of magnetic monopoles and vortices. Other
applications are related to the role of these topological excitations,
nonhomogeneous solutions of the field equations, in phase transitions
associated to spontaneous symmetry breaking in gauge theories, whose study is
of importance in phase transitions in the early universe, for instance. Here we
show a derivation of a model dual to the scalar Abelian Higgs model where its
topological excitations, namely vortex-strings, become manifest and can be
treated in a quantum field theory way. The derivation of the nontrivial
contribution of these vacuum excitations to phase transitions and its analogy
with superconductivity is then made possible and they are studied here.Comment: 7 pages. Based on a talk given by R. O. Ramos at the Infrared QCD in
Rio conference, Rio de Janeiro, Brazil, June 5-9, 200
Functional Bosonization of Non-Relativistic Fermions in Dimensions
We analyze the universality of the bosonization rules in non-relativistic
fermionic systems in . We show that, in the case of linear fermionic
dispersion relations, a general fermionic theory can be mapped into a gauge
theory in such a way that the fermionic density maps into a magnetic flux and
the fermionic current maps into a transverse electric field. These are
universal rules in the sense that they remain valid whatever the interaction
considered. We also show that these rules are universal in the case of
non-linear dispersion relations provided we consider only density-density
interactions. We apply the functional bosonization formalism to a
non-relativistic and non-local massive Thirring-like model and evaluate the
spectrum of collective excitations in several limits. In the large mass limit,
we are able to exactly calculate this spectrum for arbitrary density-density
and current-current interactions. We also analyze the massless case and show
that it has no collective excitations for any density-density potential in the
Gaussian approximation. Moreover, the presence of current interactions may
induce a gapless mode with a linear dispersion relation.Comment: 26 Pages, LaTeX, Final version to appear in International Journal of
Modern Physics
A new sequence for topological terms at any spacetime dimensions
We investigate a sequence of quadratic topological terms of the Chern-Simons
type in different spacetime dimensions, related by dimensional compactification
and sharing the properties of topological mass generation and statistical
transmutation. The implications for bosonization in several dimensions are also
analyzed.Comment: 4 pages, Revtex (multicol). To appear in Europhysics Letter
Princípios da espectroscopia no infravermelho próximo associada a imagens hiperespectrais.
Aplicações em produtos agrícolas e agroindustriais usando NIR; Espectroscopia NIR associada à imagem hiperespectral; Resolução de imagem hiperespectral NIR; Aplicações de imagens hiperespectrais NIR
Electrochemical applications of electrolytes based on ionic liquids
The potential utility of room temperature ionic liquids as
electrolytes in current electrochemical applications has been
explored. Hence, the electrochemical behavior of [Ni(tmc)]Br2
complex at a glassy carbon electrode in the absence or in the
presence of unsaturated halides in the ionic liquids, 1-ethyl-3-
methylimidazolium ethylsulfate, [C2mim][C2SO4] and N,N,Ntrimethyl-
N-(2-hydroxyethyl) ammonium
bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2], has been
examined by cyclic voltammetry. It was observed that
[Ni(tmc)]2+ complex is reduced in a reversible one-electron step
and the electrogenerated [Ni(tmc)]+ complex catalytically reduces
the carbon-halogen bond of unsaturated halides.
The potencial use of natural ionic conducting polymer
matrixes was also investigated. Samples of natural
macromolecules-based electrolytes with the ionic liquid 1-ethyl-
3-methylimidazolium ethylsulfate, [C2mim][C2SO4], were
prepared and characterized. The preliminary studies carried out
with electrochromic devices (ECDs) incorporating optimized
compositions have confirmed that these materials may perform as
satisfactory multifunctional component layers in the field of
ECD-based devices.Fundação para a Ciência e a Tecnologia (FCT
Avaliação agroeconômica de sistemas consorciados de cenoura e rúcula.
Um dos sistemas de cultivo que pode contribuir para a realização de uma agricultura sustentável economicamente é a consorciação de culturas. Estudos coprovam que rendimentos advindos de sistemas consorciados de hortaliças, apresentam-se vantajosos em relação aos obtidos nas culturas soslteiras
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