104 research outputs found
Noncommutative Geometry and Symplectic Field Theory
In this work we study representations of the Poincare group defined over
symplectic manifolds, deriving the Klein-Gordon and the Dirac equation in phase
space. The formalism is associated with relativistic Wigner functions; the
Noether theorem is derived in phase space and an interacting field, including a
gauge field, approach is discussed.Comment: To appear in Physics Letters
Finite-size effects on the chiral phase diagram of four-fermion models in four dimensions
We study the size dependence of the dynamical symmetry breaking in the
four-dimensional Nambu-Jona-Lasinio model. We show that the presence of
boundaries reduces the chiral breaking region, and this effect is strengthened
for a larger number of compactified dimensions. A critical value for the length
of the compactified dimensions exists, below which the dynamical symmetry
breaking is not possible. Considering finite temperature and chemical
potential, the chiral phase structure for the system with compactified
dimensions is obtained. A gradual decreasing of the chiral breaking region with
increasing of chemical potential is found. Also, at fixed chemical potential,
the decreasing of the size of the system changes the order of the chiral phase
transition.Comment: LATEX 14 pages 2 figure
Non-linear Liouville and Shr\"odinger equations in phase space
Unitary representations of the Galilei group are studied in phase space, in
order to describe classical and quantum systems. Conditions to write in general
form the generator of time translation and Lagrangians in phase space are then
established. In the classical case, Galilean invariance provides conditions for
writing the Liouville operator and Lagrangian for non-linear systems. We
analyze, as an example, a generalized kinetic equation where the collision term
is local and non-linear. The quantum counter-part of such unitary
representations are developed by using the Moyal (or star) product. Then a
non-linear Schr\"odinger equation in phase space is derived and analyzed. In
this case, an association with the Wigner formalism is established, which
provides a physical interpretation for the formalism
Spontaneous Symmetry Breaking in Compactified Theory
We consider the massive vector -component theory
in Euclidian space and, using an extended Matsubara formalism we perform a
compactification on a -dimensional subspace, . This allows us to
treat jointly the effect of temperature and spatial confinement in the
effective potential of the model, setting forth grounds for an analysis of
phase transitions driven by temperature and spatial boundary. For , which
corresponds to the heated system confined between two parallel planes
(separation ), we obtain, in the large limit at one-loop order, formulas
for temperature- and boundary-dependent mass and coupling constant. The
equation for the critical curve in the plane is also derived.Comment: LATEX, 11 pages no figure
Thermofield Dynamics and Casimir Effect for Fermions
A generalization of the Bogoliubov transformation is developed to describe a
space compactified fermionic field. The method is the fermionic counterpart of
the formalism introduced earlier for bosons (J. C. da Silva, A. Matos Neto, F.
C. Khanna and A. E. Santana, Phys. Rev. A 66 (2002) 052101), and is based on
the thermofield dynamics approach. We analyse the energy-momentum tensor for
the Casimir effect of a free massless fermion field in a -dimensional box at
finite temperature. As a particular case the Casimir energy and pressure for
the field confined in a 3-dimensional parallelepiped box are calculated. It is
found that the attractive or repulsive nature of the Casimir pressure on
opposite faces changes depending on the relative magnitude of the edges. We
also determine the temperature at which the Casimir pressure in a cubic boc
changes sign and estimate its value when the edge of the cybe is of the order
of confining lengths for baryons.Comment: 21 pages, 3 figures, to appear in Annals of Physic
Characteristcs chemical and soil salinization in the Irrigated District of California, SE, Brazil
O manejo inadequado da irrigação pode resultar no acúmulo de sais no solo, cuja intensidade depende da qualidade da água utilizada na irrigação, da fração de lixiviação adotada e da demanda evapotranspirativa da região. O presente trabalho teve como objetivo avaliar os atributos físicos e químicos dos solos do perímetro irrigado Califórnia, localizado no extremo noroeste do Estado de Sergipe. Para tal, foram realizadas amostragens em 42 lotes, correspondendo a 16,4% dos lotes deste perímetro. As maiores concentrações de sais e de sódio ocorreram na camada superficial (0–0,2m) do solo, o que evidenciou a falta de um manejo da irrigação adequado visando ao controle da salinidade. O aumento do pH do solo foi correlacionado significativamente com a porcentagem de sódio trocável, atingindo valores acima de 9,5. Correlações positivas significativas foram observadas entre a condutividade elétrica e os teores de Ca e Mg, indicando que sais desses íons podem estar se acumulando no solo pela ascensão do lençol freático, associado à ausência de lixiviação e drenagem. _________________________________________________________________________________________ ABSTRACT: The improper irrigation management may result in the accumulation of salts in the soil profile, which intensity depends on the irrigation water quality, the leaching fraction adopted and on the evapotranspiration demand of the region. The objective of the present study was to study the physical and chemical characteristics of the soils in the irrigated district of California, located in the northwest of the State of Sergipe. Thus, soil sampling were made in 54 lots, corresponding to 16.4% of the lots of this district. The highest salt and sodium concentrations occurred in the shallowest soil layer (0–0.2m), evidencing the lack of an appropriate irrigation management in order to control the salinity build up. The increasing of the soil pH was significantly correlated to the exchangeable sodium percentage, reaching values over 9.5. Significant positive correlations were observed between the electrical conductivity and the Ca and Mg content, indicating that salts of both ions could be accumulating in soil by the capillary rise of the water table, associated to the lack of leaching and drainage
Evaluation of electrophoretic profile and albumin quota in the cerebrospinal fluid of dogs with distemper showing or not neurvous signs
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