22,508 research outputs found
Variational Formulation for Quaternionic Quantum Mechanics
A quaternionic version of Quantum Mechanics is constructed using the
Schwinger's formulation based on measurements and a Variational Principle.
Commutation relations and evolution equations are provided, and the results are
compared with other formulations.Comment: Talk given at ICCA*, May 26-30 of 2008, Campinas, SP, Brazil. 18
pages, no figur
Superfluid and insulating phases of fermion mixtures in optical lattices
The ground state phase diagram of fermion mixtures in optical lattices is
analyzed as a function of interaction strength, fermion filling factor and
tunneling parameters. In addition to standard superfluid, phase-separated or
coexisting superfluid/excess-fermion phases found in homogeneous or
harmonically trapped systems, fermions in optical lattices have several
insulating phases, including a molecular Bose-Mott insulator (BMI), a
Fermi-Pauli (band) insulator (FPI), a phase-separated BMI/FPI mixture or a
Bose-Fermi checkerboard (BFC). The molecular BMI phase is the fermion mixture
counterpart of the atomic BMI found in atomic Bose systems, the BFC or BMI/FPI
phases exist in Bose-Fermi mixtures, and lastly the FPI phase is particular to
the Fermi nature of the constituent atoms of the mixture.Comment: 4 pages with 3 figures (Published version
Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers
We consider a nanoscale system consisting of Manganite-ferromagnet and
Cuprate-superconductor multilayers in a spin valve configuration. The
magnetization of the bottom Manganite-ferromagnet is pinned by a
Manganite-antiferromagnet. The magnetization of the top Manganite-ferromagnet
is coupled to the bottom one via indirect exchange through the superconducting
layers. We study the behavior of the critical temperature and the
magnetoresistance as a function of an externally applied parallel magnetic
field, when the number of Cuprate-superconductor layers are changed. There are
two typical behaviors in the case of a few monolayers of the Cuprates: a) For
small magnetic fields, the critical temperature and the magnetoresistance
change abruptly when the flipping field of the top Manganite-ferromagnet is
reached. b) For large magnetic fields, the multilayered system re-enters the
zero-resistance (superconducting) state after having become resistive (normal).Comment: 3 pages, 3 figures. 2004 Magnetism and Magnetic Materials Conferenc
Schwinger's Principle and Gauge Fixing in the Free Electromagnetic Field
A manifestly covariant treatment of the free quantum eletromagnetic field, in
a linear covariant gauge, is implemented employing the Schwinger's Variational
Principle and the B-field formalism. It is also discussed the abelian Proca's
model as an example of a system without constraints.Comment: 8 pages. Format PTPtex. No figur
Galactic Nonlinear Dynamic Model
We develop a model for spiral galaxies based on a nonlinear realization of
the Newtonian dynamics starting from the momentum and mass conservations in the
phase space. The radial solution exhibits a rotation curve in qualitative
accordance with the observational data.Comment: 6 pages, 1 figure. Talk given in the 7th Alexander Friedmann
International Seminar, June 29 to July 5, 2008, Joao Pessoa, PB, Brazi
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