Universal Conductance and Conductivity at Critical Points in Integer Quantum Hall Systems

The sample averaged longitudinal two-terminal conductance and the respective Kubo-conductivity are calculated at quantum critical points in the integer quantum Hall regime. In the limit of large system size, both transport quantities are found to be the same within numerical uncertainty in the lowest Landau band, $0.60\pm 0.02 e^2/h$ and $0.58\pm 0.03 e^2/h$, respectively. In the 2nd lowest Landau band, a critical conductance $0.61\pm 0.03 e^2/h$ is obtained which indeed supports the notion of universality. However, these numbers are significantly at variance with the hitherto commonly believed value $1/2 e^2/h$. We argue that this difference is due to the multifractal structure of critical wavefunctions, a property that should generically show up in the conductance at quantum critical points.Comment: 4 pages, 3 figure

Critical level spacing distribution of two-dimensional disordered systems with spin-orbit coupling

The energy level statistics of 2D electrons with spin-orbit scattering are considered near the disorder induced metal-insulator transition. Using the Ando model, the nearest-level-spacing distribution is calculated numerically at the critical point. It is shown that the critical spacing distribution is size independent and has a Poisson-like decay at large spacings as distinct from the Gaussian asymptotic form obtained by the random-matrix theory.Comment: 7 pages REVTeX, 2 uuencoded, gzipped figures; J. Phys. Condensed Matter, in prin

Log-periodic oscillations due to discrete effects in complex networks

We show that discretization of internode distribution in complex networks affects internode distances l_ij calculated as a function of degrees (k_i k_j) and an average path length as function of network size N. For dense networks there are log-periodic oscillations of above quantities. We present real-world examples of such a behavior as well as we derive analytical expressions and compare them to numerical simulations. We consider a simple case of network optimization problem, arguing that discrete effects can lead to a nontrivial solution.Comment: 5 pages, 5 figures, REVTE

Critical conductance of two-dimensional chiral systems with random magnetic flux

The zero temperature transport properties of two-dimensional lattice systems with static random magnetic flux per plaquette and zero mean are investigated numerically. We study the two-terminal conductance and its dependence on energy, sample size, and magnetic flux strength. The influence of boundary conditions and of the oddness of the number of sites in the transverse direction is also studied. We confirm the existence of a critical chiral state in the middle of the energy band and calculate the critical exponent nu=0.35 +/- 0.03 for the divergence of the localization length. The sample averaged scale independent critical conductance _c turns out to be a function of the amplitude of the flux fluctuations whereas the variance of the respective conductance distributions appears to be universal. All electronic states outside of the band center are found to be localized.Comment: to appear in Phys. Rev.

Outcomes for family medicine postgraduate training in South Africa

After 1994, the post-apartheid government decided that primary health care and the district health system would be the cornerstone of their new health policy. As a consequence of this, the academic departments of Family Medicine and primary care recognised the need for a nationally agreed set of training outcomes that were more aligned with these new priorities within the public sector. Thus in 2001, the Family Medicine Education Consortium (FaMEC), representing the eight academic departments of family medicine in South Africa, agreed to a set of outcomes for postgraduate family medicine training. At that time, all departments were running Family Medicine Master’s programmes as part-time training courses for doctors in primary health care. Recognition of the need to move towards full-time registrar training already existed, and because of this steps were taken to register Family Medicine as a speciality with the Health Professions Council of South Africa (HPCSA)

The pion mass dependence of the nucleon form-factors of the energy momentum tensor in the chiral quark-soliton model

The nucleon form factors of the energy-momentum tensor are studied in the large-Nc limit in the framework of the chiral quark-soliton model for model parameters that simulate physical situations in which pions are heavy. This allows for a direct comparison to lattice QCD results.Comment: 17 pages, 12 figure