948 research outputs found
Numerical verification of universality for the Anderson transition
We analyze the scaling behavior of the higher Lyapunov exponents at the
Anderson transition. We estimate the critical exponent and verify its
universality and that of the critical conductance distribution for box,
Gaussian and Lorentzian distributions of the random potential
Quantum interference and the spin orbit interaction in mesoscopic normal-superconducting junctions
We calculate the quantum correction to the classical conductance of a
disordered mesoscopic normal-superconducting (NS) junction in which the
electron spatial and spin degrees of freedom are coupled by an appreciable spin
orbit interaction. We use random matrix theory to describe the scattering in
the normal part of the junction and consider both quasi-ballistic and diffusive
junctions. The dependence of the junction conductance on the Schottky barrier
transparency at the NS interface is also considered. We find that the quantum
correction is sensitive to the breaking of spin rotation symmetry even when the
junction is in a magnetic field and time reversal symmetry is broken. We
demonstrate that this sensitivity is due to quantum interference between
scattering processes which involve electrons and holes traversing closed loops
in the same direction. We explain why such processes are sensitive to the spin
orbit interaction but not to a magnetic field. Finally we consider the effect
of the spin orbit interaction on the phenomenon of ``reflectionless
tunnelling.''Comment: Revised version, one new figure and revised text. This is the final
version which will appear in Journal de Physqiue 1. Latex plus six postscript
figure
Scaling of the conductance distribution near the Anderson transition
The single parameter scaling hypothesis is the foundation of our
understanding of the Anderson transition. However, the conductance of a
disordered system is a fluctuating quantity which does not obey a one parameter
scaling law. It is essential to investigate the scaling of the full conductance
distribution to establish the scaling hypothesis. We present a clear cut
numerical demonstration that the conductance distribution indeed obeys one
parameter scaling near the Anderson transition
Topology dependent quantities at the Anderson transition
The boundary condition dependence of the critical behavior for the three
dimensional Anderson transition is investigated. A strong dependence of the
scaling function and the critical conductance distribution on the boundary
conditions is found, while the critical disorder and critical exponent are
found to be independent of the boundary conditions
Symmetry, dimension and the distribution of the conductance at the mobility edge
The probability distribution of the conductance at the mobility edge,
, in different universality classes and dimensions is investigated
numerically for a variety of random systems. It is shown that is
universal for systems of given symmetry, dimensionality, and boundary
conditions. An analytical form of for small values of is discussed
and agreement with numerical data is observed. For , is
proportional to rather than .Comment: 4 pages REVTeX, 5 figures and 2 tables include
Universality of the critical conductance distribution in various dimensions
We study numerically the metal - insulator transition in the Anderson model
on various lattices with dimension (bifractals and Euclidian
lattices). The critical exponent and the critical conductance
distribution are calculated. We confirm that depends only on the {\it
spectral} dimension. The other parameters - critical disorder, critical
conductance distribution and conductance cummulants - depend also on lattice
topology. Thus only qualitative comparison with theoretical formulae for
dimension dependence of the cummulants is possible
Probability distribution of the conductance at the mobility edge
Distribution of the conductance P(g) at the critical point of the
metal-insulator transition is presented for three and four dimensional
orthogonal systems. The form of the distribution is discussed. Dimension
dependence of P(g) is proven. The limiting cases and are
discussed in detail and relation in the limit is proven.Comment: 4 pages, 3 .eps figure
Comment on the paper I. M. Suslov: Finite Size Scaling from the Self Consistent Theory of Localization
In the recent paper [I.M.Suslov, JETP {\bf 114} (2012) 107] a new scaling
theory of electron localization was proposed. We show that numerical data for
the quasi-one dimensional Anderson model do not support predictions of this
theory.Comment: Comment on the paper arXiv 1104.043
Immediate effect of kinesiology tape on ankle stability
BackgroundLateral ankle sprain is one of the most common musculoskeletal injuries, particularly among the sporting population. Due to such prevalence, many interventions have been tried to prevent initial, or further, ankle sprains. Current research shows that the use of traditional athletic tape can reduce the incidence of sprain recurrence, but this may be at a cost to athletic performance through restriction of motion. Kinesiology tape, which has become increasingly popular, is elastic in nature, and it is proposed by the manufacturers that it can correct ligament damage. Kinesiology tape, therefore, may be able to improve stability and reduce ankle sprain occurrence while overcoming the problems of traditional tape.AimTo assess the effect of kinesiology tape on ankle stability.Methods27 healthy individuals were recruited, and electromyography (EMG) measurements were recorded from the peroneus longus and tibialis anterior muscles. Recordings were taken from the muscles of the dominant leg during induced sudden ankle inversion perturbations using a custom-made tilting platform system. This was performed with and without using kinesiology tape and shoes, creating four different test conditions: barefoot(without tape), shoe(without tape), barefoot(with tape) and shoe(with tape). For each test condition, the peak muscle activity, average muscle activity and the muscle latency were calculated.ResultsNo significant difference (p>0.05) was found by using the kinesiology tape on any of the measured variables while the wearing of shoes significantly increased all the variables.ConclusionKinesiology tape has no effect on ankle stability and is unable to nullify the detrimental effects that shoes appear to have
Failure of single-parameter scaling of wave functions in Anderson localization
We show how to use properties of the vectors which are iterated in the
transfer-matrix approach to Anderson localization, in order to generate the
statistical distribution of electronic wavefunction amplitudes at arbitary
distances from the origin of disordered systems. For
our approach is shown to reproduce exact diagonalization results
available in the literature. In , where strips of width sites
were used, attempted fits of gaussian (log-normal) forms to the wavefunction
amplitude distributions result in effective localization lengths growing with
distance, contrary to the prediction from single-parameter scaling theory. We
also show that the distributions possess a negative skewness , which is
invariant under the usual histogram-collapse rescaling, and whose absolute
value increases with distance. We find for the
range of parameters used in our study, .Comment: RevTeX 4, 6 pages, 4 eps figures. Phys. Rev. B (final version, to be
published
- …