28,908 research outputs found
q-Deformed Kink Solutions
The q-deformed kink of the model is obtained via the
normalisable ground state eigenfunction of a fluctuation operator associated
with the q-deformed hyperbolic functions. From such a bosonic zero-mode the
q-deformed potential in 1+1 dimensions is found, and we show that the
q-deformed kink solution is a kink displaced away from the origin.Comment: REvtex, 11 pages, 2 figures. Preprint CBPF-NF-005/03, site at
http://www.cbpf.br. Revised version to appear in International Journal of
Modern Physics
Comment on Solution of the Relativistic Dirac-Morse Problem
We do not think that the relativistic Morse potential problem has been
correctly formulated and solved by Alhaidari (Phys. Rev. Lett. 87, 210405
(2001)).Comment: Revtex, 4 pages, preprint "Notas de F\'\i sica"
CBPF-NF-011/02/Fev./200
Modulated phases and devil's staircases in a layered mean-field version of the ANNNI model
We investigate the phase diagram of a spin- Ising model on a cubic
lattice, with competing interactions between nearest and next-nearest neighbors
along an axial direction, and fully connected spins on the sites of each
perpendicular layer. The problem is formulated in terms of a set of
noninteracting Ising chains in a position-dependent field. At low temperatures,
as in the standard mean-feild version of the Axial-Next-Nearest-Neighbor Ising
(ANNNI) model, there are many distinct spatially commensurate phases that
spring from a multiphase point of infinitely degenerate ground states. As
temperature increases, we confirm the existence of a branching mechanism
associated with the onset of higher-order commensurate phases. We check that
the ferromagnetic phase undergoes a first-order transition to the modulated
phases. Depending on a parameter of competition, the wave number of the striped
patterns locks in rational values, giving rise to a devil's staircase. We
numerically calculate the Hausdorff dimension associated with these
fractal structures, and show that increases with temperature but seems
to reach a limiting value smaller than .Comment: 17 pages, 6 figure
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