The Coulomb glass on a fractal lattice

Abstract

The single-particle density of states (DOS) is investigated for a system of localized electrons with Coulomb interaction in a random potential situated on a fractal lattice of the Vicsek type with a fractal dimension of two embedded in three-dimensional Euclidean space. To check the universality hypothesis of Efros we calculated the DOS numerically and compared it with the results for the square lattice model. We found that the DOS is determined by the geometric fractal dimension of the lattice instead of the spectral dimension, which usually determines the DOS. In particular, we found that the DOSs of the fractal lattice model and of the square lattice model show the same behaviour within the Coulomb gap provided that the ratio between the strengths of the random potential and the Coulomb interaction is identical for the two models. Thus the universality hypothesis of Efros is found to be valid with respect to different lattice structures.

Smeared phase transition in a three-dimensional Ising model with planar defects: Monte Carlo simulations

“…The approach is very similar to that of Lifshitz 38 and others developed for the description of the tails in the electronic density of states. The extremal statistics theory 36 correctly describes the leading ͑exponential͒ behavior of the magnetization and other observables. A calculation of preexponential factors would be much more complicated because one would have to include, among other things, details of the geometry of the rare regions, surface critical behavior 39,40 at the surfaces of the rare regions, and corrections to finite-size scaling.…”

“…A theory 35,36 based on extremal statistics arguments has predicted that impurities correlated in a sufficiently high number of dimensions will generically smear the phase transition. The predictions of this theory were confirmed in simulations of mean-field-type models 35,36 but up to now, a demonstration of the smearing in a more realistic short-range model has been missing.…”

“…In this section we briefly summarize the results of the extremal statistics theory 36 for the behavior in the ''tail'' of the smeared transition, i.e., in the parameter region where a few rare regions have developed static order but their density is still sufficiently low so they can be considered as independent. The approach is very similar to that of Lifshitz 38 and others developed for the description of the tails in the electronic density of states.…”

Revisión del abordaje terapéutico mediante el principio vojta sobre las alteraciones de la marcha en pacientes neurológicos

“…La locomoción refleja contiene dos patrones globales de movimiento: la reptación refleja, que se desencadena desde el decúbito prono y el volteo reflejo que lo hace desde el decúbito supino y lateral (7,11). Estos dos patrones son denominados complejos de coordinación.…”

“…La postura de activación es fuente de aferencias sobre el SNC por medio de la información propioceptiva que proporcionan músculos, articulaciones y ligamentos (11,21). Esta postura de activación induce al GCP, activando la respuesta neuronal que producen periódicamente los patrones rítmicos de locomoción (22,23).…”