Sociophysics Simulations III: Retirement Demography

This third part of the lecture series deals with the question: Who will pay for your retirement? For Western Europe the answer may be ``nobody'', but for Algeria the demography looks more promising.Comment: For 8th Granada seminar (AIP Conf. Proc.); 8 pages including 3 figure

Percolation and finite size scaling in seven dimensions

Numerical investigation of critical exponents on a hypercubic with L^d random sites with L up to $33 and d up to 7 show that above the critical dimension the phase transitions in Ising model and percolation are not alike.Comment: 5 pages including 4 figures, for Int.J.Mod.Phys.

Frequency dependent effective conductivity of two-dimensional metal-dielectric composites

We analyze a random resistor-inductor-capacitor $(RLC)$ lattice model of 2-dimensional metal-insulator composites. The results are compared with Bruggeman's and Landauer's Effective Medium Approximations where a discrepancy was observed for some frequency zones. Such a discrepancy is mainly caused by the strong conductivity fluctuations. Indeed, a two-branches distribution is observed for low frequencies. We show also by increasing the system size that at $p_c$ the so-called Drude peak vanishes; it increases for vanishing losses.Comment: 7 pages including all figures, accepted in Int. J. Mod. Phys.

Universal scaling in wildfire fractal propagation

International audienc

2D-to-3D percolation crossover of metal-insulator composites

International audiencePercolation properties and d.c. conductivity were determined for an L(2) x h-random resistor network model of metal-insulator composite films. The effects of the thickness h on the percolation threshold and conductivity were studied numerically in the limit of an infinite size of the L(2)-plane parallel to the film. For thicknesses ranging from h/L = 0.01 to h/L = 0.24, a crossover between a finite-size regime and a saturation regime was observed at h/L approximate to 0.1. In the finite-size regime (h/L >= 0.01), the percolation threshold scales as p(c)(h) - p(c3) proportional to h(-1/x), the exponent x being compatible with that of the critical exponent of the 3D correlation length, nu(3). The conductivity exponent t appeared to depend linearly on the ratio h/L with a slope nu(D) compatible with 2 + nu(2). where nu(2) is the 2D correlation length exponent. In the saturation regime, a scaling correction for the percolation threshold was found with an exponent 1 + 1/nu(3). In this regime we also observed a logarithmic dependence of the conductivity exponent on hIL. (C) 2010 Elsevier B.V. All rights reserved

Role of weighting in the dynamics of front propagation

International audienceNon-equilibrium front propagation in a two-dimensional network modelling wildfire propagation was studied. The model includes deterministic long-range interactions due to radiation and a time weighting procedure. Three weight-dependent propagation regimes were found: dynamical, static, and non-propagative. The dynamical regime shows saturation for small weight values and a percolation transition area depending on the weight and size of the interaction domain. From the scaling interface exponents, the model seems to belong to the dynamical percolation universality class. In the limit of static regime it belongs to the random deposition class. (c) 2012 Published by Elsevier B.V

Efficacité des coupures de combustible dans la prévention des feux de forêts

International audienc