17,120 research outputs found
Equivalence classes for gauge theories
In this paper we go deep into the connection between duality and fields
redefinition for general bilinear models involving the 1-form gauge field .
A duality operator is fixed based on "gauge embedding" procedure. Dual models
are shown to fit in equivalence classes of models with same fields
redefinitions
Duality and fields redefinition in three dimensions
We analyze local fields redefinition and duality for gauge field theories in
three dimensions. We find that both Maxwell-Chern-Simons and the Self-Dual
models admits the same fields redefinition. Maxwell-Proca action and its dual
also share this property. We show explicitly that a gauge-fixing term has no
influence on duality and fields redefinition.Comment: 8 pages, suppressed contents. To appear in J. Phys.
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
Riccati-type equations, generalised WZNW equations, and multidimensional Toda systems
We associate to an arbitrary -gradation of the Lie algebra of a
Lie group a system of Riccati-type first order differential equations. The
particular cases under consideration are the ordinary Riccati and the matrix
Riccati equations. The multidimensional extension of these equations is given.
The generalisation of the associated Redheffer--Reid differential systems
appears in a natural way. The connection between the Toda systems and the
Riccati-type equations in lower and higher dimensions is established. Within
this context the integrability problem for those equations is studied. As an
illustration, some examples of the integrable multidimensional Riccati-type
equations related to the maximally nonabelian Toda systems are given.Comment: LaTeX2e, 18 page
Plastic Deformation of 2D Crumpled Wires
When a single long piece of elastic wire is injected trough channels into a
confining two-dimensional cavity, a complex structure of hierarchical loops is
formed. In the limit of maximum packing density, these structures are described
by several scaling laws. In this paper it is investigated this packing process
but using plastic wires which give origin to completely irreversible structures
of different morphology. In particular, it is studied experimentally the
plastic deformation from circular to oblate configurations of crumpled wires,
obtained by the application of an axial strain. Among other things, it is shown
that in spite of plasticity, irreversibility, and very large deformations,
scaling is still observed.Comment: 5 pages, 6 figure
The 1/N Expansion in Noncommutative Quantum Mechanics
We study the 1/N expansion in noncommutative quantum mechanics for the
anharmonic and Coulombian potentials. The expansion for the anharmonic
oscillator presented good convergence properties, but for the Coulombian
potential, we found a divergent large N expansion when using the usual
noncommutative generalization of the potential. We proposed a modified version
of the noncommutative Coulombian potential which provides a well-behaved 1/N
expansion.Comment: v2: resided version, to appear in PRD, 18 pages, 4 figure
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