9,345 research outputs found
Avaliação Biológica de Viroses em Plantas Matrizes e Mudas de Batata-doce (Ipomoea batatas).
bitstream/item/30878/1/Circular-75.pd
Spinor Fields Classification in Arbitrary Dimensions and New Classes of Spinor Fields on 7-Manifolds
A classification of spinor fields according to the associated bilinear
covariants is constructed in arbitrary dimensions and metric signatures,
generalizing Lounesto's 4D spinor field classification. In such a generalized
classification a basic role is played by the geometric Fierz identities. In 4D
Minkowski spacetime the standard bilinear covariants can be either null or
non-null -- with the exception of the current density which is invariably
different from zero for physical reasons -- and sweep all types of spinor
fields, including Dirac, Weyl, Majorana and more generally flagpoles,
flag-dipoles and dipole spinor fields. To obtain an analogous classification in
higher dimensions we use the Fierz identities, which constrain the covariant
bilinears in the spinor fields and force some of them to vanish. A generalized
graded Fierz aggregate is moreover obtained in such a context simply from the
completeness relation. We analyze the particular and important case of
Riemannian 7-manifolds, where the Majorana spinor fields turn out to have a
quite special place. In particular, at variance with spinor fields in 4D
Minkowski spacetime that are classified in six disjoint classes, spinors in
Riemannian 7-manifolds are shown to be classified, according to the bilinear
covariants: (a) in just one class, in the real case of Majorana spinors; (b) in
four classes, in the most general case. Much like new classes of spinor fields
in 4D Minkowski spacetime have been evincing new possibilities in physics, we
think these new classes of spinor fields in seven dimensions are, in
particular, potential candidates for new solutions in the compactification of
supergravity on a seven-dimensional manifold and its exotic versions.Comment: 15 page
Microscopia eletrônica de varredura.
bitstream/CPACT-2009-09/11940/1/microscopia_eletronica.pd
Procedimento de visualização e avaliação do fungo Darluca filum em folhas de ameixeira, utilizando microscopia eletrônica.
bitstream/item/31642/1/comunicado109.pd
Meyer: híbrido de citros com propriedades de limoeiro e morfologia de laranjeira.
bitstream/item/53715/1/MEYER-HIBRIDO-DE-CITROS.pdfCNPQ; FEPAGRO
Flame: pomelo de polpa bem vermelha e sem sementes.
bitstream/item/53714/1/FLAME-POMELO-DE-POLPA.pdfCNPQ, FEPAGRO
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