81,042 research outputs found
On the -Dirac Oscillator revisited
This Letter is based on the -Dirac equation, derived from the
-Poincar\'{e}-Hopf algebra. It is shown that the -Dirac
equation preserves parity while breaks charge conjugation and time reversal
symmetries. Introducing the Dirac oscillator prescription,
, in the -Dirac
equation, one obtains the -Dirac oscillator. Using a decomposition in
terms of spin angular functions, one achieves the deformed radial equations,
with the associated deformed energy eigenvalues and eigenfunctions. The
deformation parameter breaks the infinite degeneracy of the Dirac oscillator.
In the case where , one recovers the energy eigenvalues and
eigenfunctions of the Dirac oscillator.Comment: 5 pages, no figures, accepted for publication in Physics Letters
Brane Cosmic String Compactification in Brans-Dicke Theory
We investigate an alternative compactification of extra dimensions using
local cosmic string in the Brans-Dicke gravity framework. In the context of
dynamical systems it is possible to show that there exist a stable field
configuration for the Einstein-Brans-Dicke equations. We explore the analogies
between this particular model and the Randall-Sundrum scenario.Comment: RevTex, 5 pages, no figures. To appear in the Physical Review
Towards an hybrid compactification with a scalar-tensor global cosmic string
We derive a solution of the gravitational equations which leads to a
braneworld scenario in six dimensions using a global cosmic string solution in
a low energy effective string theory framework. The final spacetime is composed
by one warped brane with topology and a power
law warp factor, and one noncompact extra dimension transverse to the brane. By
looking at the current experimental bounds, we find a range of parameters in
which, if the on-brane dimension has an acceptable size, it does not solve the
hierarchy problem. In another example this problem is smoothed by the
Brans-Dicke parameter.Comment: RevTex, 7 pages. New version to be published in the JCAP (2008
Characterizing Weak Chaos using Time Series of Lyapunov Exponents
We investigate chaos in mixed-phase-space Hamiltonian systems using time
series of the finite- time Lyapunov exponents. The methodology we propose uses
the number of Lyapunov exponents close to zero to define regimes of ordered
(stickiness), semi-ordered (or semi-chaotic), and strongly chaotic motion. The
dynamics is then investigated looking at the consecutive time spent in each
regime, the transition between different regimes, and the regions in the
phase-space associated to them. Applying our methodology to a chain of coupled
standard maps we obtain: (i) that it allows for an improved numerical
characterization of stickiness in high-dimensional Hamiltonian systems, when
compared to the previous analyses based on the distribution of recurrence
times; (ii) that the transition probabilities between different regimes are
determined by the phase-space volume associated to the corresponding regions;
(iii) the dependence of the Lyapunov exponents with the coupling strength.Comment: 8 pages, 6 figure
The Jacobi identity for Dirac-like brackets
For redundant second-class constraints the Dirac brackets cannot be defined
and new brackets must be introduced. We prove here that the Jacobi identity for
the new brackets must hold on the surface of the second-class constraints. In
order to illustrate our proof we work out explicitly the cases of a fractional
spin particle in 2+1 dimensions and the original Brink-Schwarz massless
superparticle in D=10 dimensions in a Lorentz covariant constraints separation.Comment: 14 pages, Latex. Final version to be published in Int. J. Mod. Phys.
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