253 research outputs found
Canonical Transformations in a Higher-Derivative Field Theory
It has been suggested that the chiral symmetry can be implemented only in
classical Lagrangians containing higher covariant derivatives of odd order.
Contrary to this belief, it is shown that one can construct an exactly soluble
two-dimensional higher-derivative fermionic quantum field theory containing
only derivatives of even order whose classical Lagrangian exhibits chiral-gauge
invariance. The original field solution is expressed in terms of usual Dirac
spinors through a canonical transformation, whose generating function allows
the determination of the new Hamiltonian. It is emphasized that the original
and transformed Hamiltonians are different because the mapping from the old to
the new canonical variables depends explicitly on time. The violation of
cluster decomposition is discussed and the general Wightman functions
satisfying the positive-definiteness condition are obtained.Comment: 12 pages, LaTe
Resposta do dendezeiro à aplicação de fertilizantes nas condições do Estado do Amazonas.
O presente trabalho visa estudar o efeito da adubação nitrogenada, fosfatada, potássica e magnesiana no desenvolvimento e na produção do dendezeiro.bitstream/item/89200/1/PA-08-Maria-do-Rosario.pd
Ponte Verde para Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) em Terras Baixas.
bitstream/item/126188/1/Comunicado-317.pd
Produção de mudas de dendezeiro na Amazônia.
A fase de produção de mudas tem como objetivo a obtenção de plantas de alta qualidade agronômica e em condições para serem levadas ao campo na época mais apropriada, considerando o regime de chuvas na região.bitstream/item/113947/1/ct-8-producao-de-mudas-de-dendezeiro-no-am.pd
Symmetry transform in the Faddeev-Jackiw quantization of dual models
We study the presence of symmetry transformations in the Faddeev-Jackiw
approach for constrained systems. Our analysis is based in the case of a
particle submitted to a particular potential which depends on an arbitrary
function. The method is implemented in a natural way and symmetry generators
are identified. These symmetries permit us to obtain the absent elements of the
sympletic matrix which complement the set of Dirac brackets of such a theory.
The study developed here is applied in two different dual models. First, we
discuss the case of a two-dimensional oscillator interacting with an
electromagnetic potential described by a Chern-Simons term and second the
Schwarz-Sen gauge theory, in order to obtain the complete set of non-null Dirac
brackets and the correspondent Maxwell electromagnetic theory limit.Comment: 22 pages, RevTex file, no figur
A new picture on (3+1)D topological mass mechanism
We present a class of mappings between the fields of the Cremmer-Sherk and
pure BF models in 4D. These mappings are established by two distinct
procedures. First a mapping of their actions is produced iteratively resulting
in an expansion of the fields of one model in terms of progressively higher
derivatives of the other model fields. Secondly an exact mapping is introduced
by mapping their quantum correlation functions. The equivalence of both
procedures is shown by resorting to the invariance under field scale
transformations of the topological action. Related equivalences in 5D and 3D
are discussed. A cohomological argument is presented to provide consistency of
the iterative mapping.Comment: 13 page
Schild's Null Strings in Flat and Curved Backgrounds
Schild's null (tensionless) strings are discussed in certain flat and curved
backgrounds. We find closed, stationary, null strings as natural configurations
existing on the horizons of spacetimes which possess such null hypersurfaces.
Examples of these are obtained in Schwarzschild and Rindler spacetimes. A
dynamic null string is also identified in Rindler spacetime. Furthermore, a
general prescription (with explicit examples) is outlined by means of which
null string configurations can be obtained in a large class of cosmological
backgrounds.Comment: RevTex 3.0, 14 Pages, no figure
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