24,508 research outputs found
Generalized Miura Transformations, Two-Boson KP Hierarchies and their Reduction to KDV Hierarchies
Bracket preserving gauge equivalence is established between several two-boson
generated KP type of hierarchies. These KP hierarchies reduce under symplectic
reduction (via Dirac constraints) to KdV, mKdV and Schwarzian KdV hierarchies.
Under this reduction the gauge equivalence is taking form of the conventional
Miura maps between the above KdV type of hierarchies.Comment: 12 pgs., LaTeX, IFT-P/011/93, UICHEP-TH/93-
Supersymmetric Construction of W-Algebras from Super Toda and Wznw Theories
A systematic construction of super W-algebras in terms of the WZNW model
based on a super Lie algebra is presented. These are shown to be the symmetry
structure of the super Toda models, which can be obtained from the WZNW theory
by Hamiltonian reduction. A classification, according to the conformal spin
defined by an improved energy-momentum tensor, is dicussed in general terms for
all super Lie algebras whose simple roots are fermionic . A detailed discussion
employing the Dirac bracket structure and an explicit construction of
W-algebras for the cases of , , and are given. The and super conformal algebras are discussed
in the pertinent cases.Comment: 24 page
Exact static soliton solutions of 3+1 dimensional integrable theory with nonzero Hopf numbers
In this paper we construct explicitly an infinite number of Hopfions (static,
soliton solutions with non-zero Hopf topological charges) within the recently
proposed 3+1-dimensional, integrable and relativistically invariant field
theory. Two integers label the family of Hopfions we have found. Their product
is equal to the Hopf charge which provides a lower bound to the soliton's
finite energy. The Hopfions are constructed explicitly in terms of the toroidal
coordinates and shown to have a form of linked closed vortices.Comment: LaTeX, 7 pg
Building analytical three-field cosmological models
A difficult task to deal with is the analytical treatment of models composed
by three real scalar fields, once their equations of motion are in general
coupled and hard to be integrated. In order to overcome this problem we
introduce a methodology to construct three-field models based on the so-called
"extension method". The fundamental idea of the procedure is to combine three
one-field systems in a non-trivial way, to construct an effective three scalar
field model. An interesting scenario where the method can be implemented is
within inflationary models, where the Einstein-Hilbert Lagrangian is coupled
with the scalar field Lagrangian. We exemplify how a new model constructed from
our method can lead to non-trivial behaviors for cosmological parameters.Comment: 11 pages, and 3 figures, updated version published in EPJ
Sorção, dessorção e potencial de lixiviação de atrazine em solos brasileiros.
Determinar a sorção, a dessorção e o potencial de lixiviação de atrazine em diferentes solos, foram os objetivos desse trabalho. As amostras dos solos foram agitadas por 24 h, centrifugadas e o sobrenadante filtrado e analisado por HPLC. As etapas da dessorção foram conduzidas por meio da reposição do sobrenadante removido com o mesmo volume de solução 0,01 M de CaCl2 com agitação por 24h e centrifugação, repetindo-se o processo por três vezes consecutivas, 24, 48 e 72 h, sendo o sobrenadante filtrado e analisado por HPLC. A sorção de atrazine, descrita pela isoterma de Freundlich, foi calculada pela diferença entre as concentrações adicionadas e aquelas quantificadas no HPLC. Foram calculadas as percentagens de dessorção a 24, 48 e 72 h pela diferença entre as quantidades sorvidas e aquelas quantificadas no HPLC. Correlações de Pearson foram feitas para se determinar a correlação entre kf, kfoc e dessorção e as principais propriedades dos solos. O coeficiente GUS foi utilizado para estimar o potencial de lixiviação. Os baixos valores encontrados para o kf da atrazine indicam que esse herbicida é de pequena sorção pelos solos estudados. No perfil LVd-a a sorção se correlacionou significativa e positivamente com o teor de carbono orgânico quando analisado isoladamente. Os valores de kfoc variaram de 70,37 a 201,47 nas amostras superficiais dos solos estudados e apresentaram correlação significativa com o teor de carbono orgânico quando analisado somente o perfil do LVd-a. A avaliação do potencial de lixiviação demonstrou que a atrazine pode ser classificada como herbicida lixiviador em todos os solos analisados. O processo de dessorção foi menor que o processo de sorção até 72 horas após a aplicação. A dessorção é maior em camadas mais profundas no perfil do solo LVd-a, onde o teor de carbono orgânico é menor
Scattering of Dirac particles from non-local separable potentials: the eigenchannel approach
An application of the new formulation of the eigenchannel method [R.
Szmytkowski, Ann. Phys. (N.Y.) {\bf 311}, 503 (2004)] to quantum scattering of
Dirac particles from non-local separable potentials is presented. Eigenchannel
vectors, related directly to eigenchannels, are defined as eigenvectors of a
certain weighted eigenvalue problem. Moreover, negative cotangents of
eigenphase-shifts are introduced as eigenvalues of that spectral problem.
Eigenchannel spinor as well as bispinor harmonics are expressed throughout the
eigenchannel vectors. Finally, the expressions for the bispinor as well as
matrix scattering amplitudes and total cross section are derived in terms of
eigenchannels and eigenphase-shifts. An illustrative example is also provided.Comment: Revtex, 9 pages, 4 figures, published versio
Non-exponential relaxation for anomalous diffusion
We study the relaxation process in normal and anomalous diffusion regimes for
systems described by a generalized Langevin equation (GLE). We demonstrate the
existence of a very general correlation function which describes the relaxation
phenomena. Such function is even; therefore, it cannot be an exponential or a
stretched exponential. However, for a proper choice of the parameters, those
functions can be reproduced within certain intervals with good precision. We
also show the passage from the non-Markovian to the Markovian behaviour in the
normal diffusion regime. For times longer than the relaxation time, the
correlation function for anomalous diffusion becomes a power law for broad-band
noise.Comment: 6 pages, 2 figure
Uso de fosfato natural no cultivo de arroz, soja e milho em rotação, no sistema plantio direto.
bitstream/item/43871/1/boletim-20.pd
Transport Properties of Highly Aligned Polymer Light-Emitting-Diodes
We investigate hole transport in polymer light-emitting-diodes in which the
emissive layer is made of liquid-crystalline polymer chains aligned
perpendicular to the direction of transport. Calculations of the current as a
function of time via a random-walk model show excellent qualitative agreement
with experiments conducted on electroluminescent polyfluorene demonstrating
non-dispersive hole transport. The current exhibits a constant plateau as the
charge carriers move with a time-independent drift velocity, followed by a long
tail when they reach the collecting electrode. Variation of the parameters
within the model allows the investigation of the transition from non-dispersive
to dispersive transport in highly aligned polymers. It turns out that large
inter-chain hopping is required for non-dispersive hole transport and that
structural disorder obstructs the propagation of holes through the polymer
film.Comment: 4 pages, 5 figure
Aether field coupled to the electromagnetic field in the TFD formalism
In this paper, the aether field, which leads to the violation of Lorentz
symmetries, coupled with the electromagnetic field is considered. In order to
study thermal and size effects in this theory, the Thermo Field Dynamics (TFD)
formalism is used. TFD is a real-time quantum field theory that has an
interesting topological structure. Here three different topologies are taken,
then three different phenomena are calculated. These effects are investigated
considering that the aether field can point in different directions. The
results obtained are compared with the usual results of the Lorentz invariant
electromagnetic field.Comment: 15 pages, accepted for publication in EPJ
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