43,223 research outputs found
Noncommutativity due to spin
Using the Berezin-Marinov pseudoclassical formulation of spin particle we
propose a classical model of spin noncommutativity. In the nonrelativistic
case, the Poisson brackets between the coordinates are proportional to the spin
angular momentum. The quantization of the model leads to the noncommutativity
with mixed spacial and spin degrees of freedom. A modified Pauli equation,
describing a spin half particle in an external e.m. field is obtained. We show
that nonlocality caused by the spin noncommutativity depends on the spin of the
particle; for spin zero, nonlocality does not appear, for spin half, , etc. In the relativistic case the noncommutative
Dirac equation was derived. For that we introduce a new star product. The
advantage of our model is that in spite of the presence of noncommutativity and
nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation
it gives noncommutativity with a nilpotent parameter.Comment: 11 pages, references adda
Altura de corte das plantas e perda de feijão com colhedora automotriz axial.
Este trabalho teve como objetivo avaliar o desempenho de uma colhedora automotriz axial, submetida a três velocidades de operação, em dois períodos de colheita de duas cultivares de feijão
Plantio direto do arroz influenciado por tipos de sulcadores e compactadores de sulcos da semeadora adubadora.
Este trabalho teve o objetivo de estudar o efeito de diferentes configurações de sulcadores e de compactadores numa semeadora adubadora sobre o estabelecimento e a produtividade da cultura do arroz de terras altas em solo sob plantio direto.bitstream/CNPAF/23005/1/comt_81.pd
Limits on dark matter proton scattering from neutrino telescopes using micrOMEGAs
Limits on dark matter spin dependent elastic scattering cross section on
protons derived from IceCube data are obtained for different dark matter
annihilation channels using micrOMEGAs. The uncertainty on the derived limits,
estimated by using different neutrino spectra, can reach a factor two. For all
dark matter annihilation channels except for quarks, the limits on the spin
dependent cross section are more stringent than those obtained in direct
detection experiments. The new functions that allow to derive those limits are
described.Comment: 23 pages, 7 figures; v2: references added; v3 and v4: clarifications
added; The code can be downloaded from https://lapth.cnrs.fr/micromega
Avaliação da produtividade das ordens primária, secundária e terciária de genótipos de mamoneira de porte baixo em Irecê-BA.
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