19,821 research outputs found

    Anisotropy and percolation threshold in a multifractal support

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    Recently a multifractal object, QmfQ_{mf}, was proposed to study percolation properties in a multifractal support. The area and the number of neighbors of the blocks of QmfQ_{mf} show a non-trivial behavior. The value of the probability of occupation at the percolation threshold, pcp_{c}, is a function of ρ\rho, a parameter of QmfQ_{mf} which is related to its anisotropy. We investigate the relation between pcp_{c} and the average number of neighbors of the blocks as well as the anisotropy of QmfQ_{mf}

    On the choice of parameters in solar structure inversion

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    The observed solar p-mode frequencies provide a powerful diagnostic of the internal structure of the Sun and permit us to test in considerable detail the physics used in the theory of stellar structure. Amongst the most commonly used techniques for inverting such helioseismic data are two implementations of the optimally localized averages (OLA) method, namely the Subtractive Optimally Localized Averages (SOLA) and Multiplicative Optimally Localized Averages (MOLA). Both are controlled by a number of parameters, the proper choice of which is very important for a reliable inference of the solar internal structure. Here we make a detailed analysis of the influence of each parameter on the solution and indicate how to arrive at an optimal set of parameters for a given data set.Comment: 14 pages, 15 figures. Accepted for publication on MNRA

    Precise calculation of the threshold of various directed percolation models on a square lattice

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    Using Monte Carlo simulations on different system sizes we determine with high precision the critical thresholds of two families of directed percolation models on a square lattice. The thresholds decrease exponentially with the degree of connectivity. We conjecture that pcp_{c} decays exactly as the inverse of the coodination number.Comment: 2 pages, 2 figures and 1 tabl
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