16,070 research outputs found
Causal Structure and Birefringence in Nonlinear Electrodynamics
We investigate the causal structure of general nonlinear electrodynamics and
determine which Lagrangians generate an effective metric conformal to
Minkowski. We also proof that there is only one analytic nonlinear
electrodynamics presenting no birefringence.Comment: 11 pages, no figure
Remarks on Charged Vortices in the Maxwell-Chern-Simons Model
We study vortex-like configuration in Maxwell-Chern-Simons Electrodynamics.
Attention is paid to the similarity it shares with the Nielsen-Olesen solutions
at large distances. A magnetic symmetry between a point-like and an
azimuthal-like current in this framework is also pointed out. Furthermore, we
address the issue of a neutral and spinless particle interacting with a charged
vortex, and obtain that the Aharonov-Casher-type phase depends upon mass and
distance parameters.Comment: New refs. added. Version accepted for publication in Phys. Lett.
Ultra-cold fermions in real or fictitious magnetic fields: The BCS-BEC evolution and the type-I--type-II transition
We study ultra-cold neutral fermion superfluids in the presence of fictitious
magnetic fields, as well as charged fermion superfluids in the presence of real
magnetic fields. Charged fermion superfluids undergo a phase transition from
type-I to type-II superfluidity, where the magnetic properties of the
superfluid change from being a perfect diamagnet without vortices to a partial
diamagnet with the emergence of the Abrikosov vortex lattice. The transition
from type-I to type-II superfluidity is tunned by changing the scattering
parameter (interaction) for fixed density. We also find that neutral fermion
superfluids such as Li and K are extreme type-II superfluids, and
that they are more robust to the penetration of a fictitious magnetic field in
the BCS-BEC crossover region near unitarity, where the critical fictitious
magnetic field reaches a maximum as a function of the scattering parameter
(interaction).Comment: 4+ pages with 2 figure
Genetic gain in an improvement program of irrigated rice in Minas Gerais.
An evaluation of the genetic improvement programme of irrigated rice of Minas Gerais (Brazil) estimated the genetic gain obtained in the 90s. Grain yield data of the advanced comparative trials of cultivars and lines of continuously flooded rice, conducted from 1990-91 to 2000-01, were used. The estimate of the genetic gain was obtained by the methodology of the adjusted means proposed by Breseghello (1998). The mean annual genetic gain in the 90s was 42.45+or-17.89 kg ha-1 (0.7% per year). The improvement programme proved auspicious for the development of lines that outmatched the controls. The mean of the cultivars released in the 90s did however not outstrip the mean of the elite lines, which were the genotypes with the highest means in this study and will be further evaluated in the ongoing programme
Quantum Non-Demolition Test of Bipartite Complementarity
We present a quantum circuit that implements a non-demolition measurement of
complementary single- and bi-partite properties of a two-qubit system:
entanglement and single-partite visibility and predictability. The system must
be in a pure state with real coefficients in the computational basis, which
allows a direct operational interpretation of those properties. The circuit can
be realized in many systems of interest to quantum information.Comment: 4 pages, 2 figure
Electromagnetic structure and weak decay of pseudoscalar mesons in a light-front QCD-inspired model
We study the scaling of the meson mass splitting and the
pseudoscalar weak decay constants with the mass of the meson, as seen in the
available experimental data. We use an effective light-front QCD-inspired
dynamical model regulated at short-distances to describe the valence component
of the pseudoscalar mesons. The experimentally known values of the mass
splittings, decay constants (from global lattice-QCD averages) and the pion
charge form factor up to 4 [GeV/c] are reasonably described by the modelComment: 27 Pages, 7 eps figures,use revtex
A model for structural defects in nanomagnets
A model for describing structural pointlike defects in nanoscaled
ferromagnetic materials is presented. Its details are explicitly developed
whenever interacting with a vortex-like state comprised in a thin nanodisk.
Among others, our model yields results for the vortex equilibrium position
under the influence of several defects along with an external magnetic field in
good qualitative agreement with experiments. We also discuss how such defects
may affect the vortex motion, like its gyrotropic oscillation and dynamical
polarization reversal.Comment: 8 pages, resubmitted to Journal of Applied Physic
Análise da viabilidade econômica do cultivo do feijão-comum, safra 2013, em Mato Grosso do Sul.
bitstream/item/76338/1/COT2012183.pd
Weak decay constant of pseudscalar meson in a QCD-inspired model
We show that a linear scaling between the weak decay constants of
pseudoscalar and the vector mesons masses is supported by the available
experimental data. The decay constant scale as (f_m
is decay constant and M_V vector meson ground state mass). This simple form is
justified within a renormalized light-front QCD-inpired model for
quark-antiquark bound states.Comment: 4 pages, use revtex style. To appear "Brazilian Journal of Physics
(2003)
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