10,459 research outputs found
Self-Diffusion in Simple Models: Systems with Long-Range Jumps
We review some exact results for the motion of a tagged particle in simple
models. Then, we study the density dependence of the self diffusion
coefficient, , in lattice systems with simple symmetric exclusion in
which the particles can jump, with equal rates, to a set of neighboring
sites. We obtain positive upper and lower bounds on
for .
Computer simulations for the square, triangular and one dimensional lattice
suggest that becomes effectively independent of for .Comment: 24 pages, in TeX, 1 figure, e-mail addresses: [email protected],
[email protected], [email protected]
Four-dimensional gravity on supersymmetric dilatonic domain walls
We investigate the localization of four-dimensional metastable gravity in
supersymmetric dilatonic domain walls through massive modes by considering
several scenarios in the model. We compute corrections to the Newtonian
potential for small and long distances compared with a crossover scale given in
terms of the dilatonic coupling. 4D gravity behavior is developed on the brane
for distance very much below the crossover scale, while for distance much
larger, the 5D gravity is recovered. Whereas in the former regime gravity is
always attractive, in the latter regime due to non-normalizable unstable
massive graviton modes present on the spectrum, in some special cases, gravity
appears to be repulsive and signalizes a gravitational confining phase which is
able to produce an inflationary phase of the Universe.Comment: 11 pages, 4 figures, Latex. Version to appear in PL
Analytical Multi-kinks in smooth potentials
In this work we present an approach which can be systematically used to
construct nonlinear systems possessing analytical multi-kink profile
configurations. In contrast with previous approaches to the problem, we are
able to do it by using field potentials which are considerably smoother than
the ones of Doubly Quadratic family of potentials. This is done without losing
the capacity of writing exact analytical solutions. The resulting field
configurations can be applied to the study of problems from condensed matter to
brane world scenarios
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