International Journal of Modern Physics C

The genetic algorithm (M. Iwamatsu, J. Chem. Phys.112, 10976 (2000)), which combines the space-fixed genetic algorithm of Niesse and Mayne (J. Chem. Phys.105, 4700 (1996)) with simplex local minimization method is generalized to handle the conformation optimization of binary mixed clusters. This genetic algorithm based on real coding can successfully find the lowest energy structure of mixed argon–xenon alloys Ar_xXe_13-x and confirms the results found by other methods.

We implement the so-called "complex-plane iterative technique" (CIT) to the computation of classical differentially rotating magnetic white dwarf and neutron star models. The program has been written in SCILAB (© INRIA-ENPC), a matrix-oriented high-level programming language, which can be downloaded free of charge from the site . Due to the advanced capabilities of this language, the code is short and understandable. Highlights of the program are: (a) time-saving character, (b) easy use due to the built-in graphics user interface, (c) easy interfacing with Fortran via online dynamic link. We interpret our numerical results in various ways by extensively using the graphics environment of SCILAB.

The Sznajd model, where two people having the same opinion can convince their neighbors on the square lattice, is modified in the sense of Deffuant et al. and Hegselmann, that only neighbors of similar opinions can be convinced. Then consensus is easy for the competition of up to three opinions but difficult for four and more opinions.

The restructuring process of diagenesis in the sedimentary rocks is studied using a percolation type model. The cementation and dissolution processes are modeled by the culling of occupied sites in rarefied and growth of vacant sites in dense environments. Starting from sub-critical states of ordinary percolation the system evolves under the diagenetic rules to critical percolation configurations. Our numerical simulation results in two dimensions indicate that the stable configuration has the same critical behavior as the ordinary percolation.

The question we address here is of whether phenomena of collective bankruptcies are related to self-organized criticality. In order to answer it we propose a simple model of banking networks based on the random directed percolation. We study effects of one bank failure on the nucleation of contagion phase in a financial market. We recognize the power law distribution of contagion sizes in 3d- and 4d-networks as an indicator of SOC behavior. The SOC dynamics was not detected in 2d-lattices. The difference between 2d- and 3d- or 4d-systems is explained due to the percolation theory.

We discuss hybrid Monte Carlo algorithms for odd-flavor lattice QCD simulations. The algorithms include a polynomial approximation, which enables us to simulate odd-flavor QCD in the framework of the hybrid Monte Carlo algorithm. In order to make the algorithms exact, the correction factor to the polynomial approximation is also included in an economical, stochastic way. We test the algorithms for n_f = 1, 1 + 1 and 2 + 1 flavors and compare results with other algorithms.

The formation of carbon nanorods from various types of carbon nanotubes has been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanorod formed from carbon nanotubes with different chirality is not stable even at low temperature.

The Floating Spherical Gaussian Orbital (FSGO) closed-shell energy analytic third derivative with respect to nuclear displacement is presented here. In order to save computational time, the formulas for the third derivative of electron nuclear attraction are written in terms of original integrals. Although the formulas were presented in general for any type of application, the FSGO method is applied to H₂O and CH₂ molecules in singlet ground electronic state. Besides the accuracy of analytical derivative, the saving in computational time is significant.

Bond-percolation processes are studied for random lattices on the surface of a sphere, and for their duals. The estimated threshold is 0.3326 ± 0.0005 for spherical random lattices and 0.6680 ± 0.0005 for the duals of spherical random lattices, and the exact threshold is conjectured as 1/3 for two-dimensional random lattices and 2/3 for their duals. A suitably defined spanning probability at the threshold, E_p(p_c), for both spherical random lattices and their duals is 0.980±0.005, which may be universal for a 2-d lattice with this spanning definition. The shift-to-width ratio of the distribution function of the threshold concentration and the universal values of the critical value of the effective coordination number can be extended from regular lattices to spherical random lattices and their duals. The results of critical exponents are consistent with the assertion from the universality hypothesis. Finite-size scaling is also examined.

The fine structure energies and fine structure splittings of some low-lying excited states of the beryllium isoelectronic sequence (Z = 4–20) are calculated with multi-configuration-interaction method and restricted variation method. The relativistic corrections and mass polarization are included. The results are in good agreement with other theoretical and experimental data.

We study the resonant behavior of a system consisting of a square array of multi-coated cylinders by calculating the effective dielectric constant of the system. The results were examined numerically using the finite element method.

We study the relation between stock price changes and the difference in the volume of sell and buy orders. Using a soft spin model, we describe the price impact of order imbalances and find an analogy to the fluctuation–dissipation theorem in physical systems. We empirically investigate fluctuations and market friction for a major US stock and find support for our model calculations.