International Journal of Modern Physics C

This paper investigates the topological properties of bank networks. We build the minimum spanning tree, which is based on the concept of ultrametricity, using the correlation matrix for a variety of banking variables. Empirical results suggest that the private and foreign banks tend to form clusters within the network. Furthermore, banks with different sizes are also strongly connected and tend to form clusters. These results are robust to the use of different variables to build the network, such as bank profitability, assets, equity, revenue and loans.

Isothermal gas flow in microtubes with a sudden expansion or contraction is studied numerically by lattice Boltzmann method. An axisymmetric D2Q9 model is used to simulate gas slip flow in micro-circular pipes. With the boundary condition combined specular and bounce-back schemes, the computed results are in excellent agreement with analytical solution for straight microtube. For the gas flow in the expanded or constricted tubes, we carried out simulations of several Knudsen numbers with inlet/outlet pressure ratio 3. It is found the pressure drop in each section can be predicted well by the theory of straight tubes. For smaller Knudsen number, flow separation in the expanded tube is observed. While for large Knudsen number, there is no vortex at corner and the streamlines are attached to boundary. In the constricted tube, the vortex at corner is very weak. These results are consistent with some experimental conclusions.

Quantum states can be described equivalently by density matrices, Wigner functions, or quantum tomograms. We analyze the accuracy and performance of three related semiclassical approaches to quantum dynamics, in particular with respect to their numerical implementation. As test cases, we consider the time evolution of Gaussian wave packets in different one-dimensional geometries, whereby tunneling, resonance, and anharmonicity effects are taken into account. The results and methods are benchmarked against an exact quantum mechanical treatment of the system, which is based on a highly efficient Chebyshev expansion technique of the time evolution operator.

In this work, we show that an adequate modulation of the driving amplitude in an anharmonic chain results in an efficient transmission of binary information. The nonlinear processes of supratransmission and infratransmission are shown to be useful in the solution of the problem under investigation. Numerical results are conducted using a finite-difference scheme with consistency properties in the energy domain, and the experiments show that localized nonlinear modes are propagated through the chain in a reliable and controlled manner.

The transport of particles in two-dimensional self-affine rough channels is investigated through numerical simulations. We show how the average transit time depends on the particle Stokes number as well as on the restitution coefficient controlling the collisions with the walls. More precisely, our results reveal that the particle motion in such irregular channels displays a complex behavior that is characterized by the existence of four distinct transit time regimes. Finally, we also show that this rich behavior is a direct consequence of the local competition between particle-structure (collisions) and particle-fluid (drag) interactions taking place in the system.

Numerical simulation and analysis of long-range correlations in curved space are studied. The study is motivated by the problem of constructing accurate models of large-scale porous media which usually contain long-range correlations in their various properties (such as their permeability, porosity, and elastic moduli) within and between their strata that are typically curved layers. The problem is, however, relevant to many other important models and phenomena in which extended correlations in curved space play a prominent role. Examples include the nonlinear σ-model in a curved space, models for describing the long-range structural correlations of amorphous semiconductors that consist of polytopes (tilings of positively-curved three-dimensional space), long-range correlations in the extrapolar total zone, and models in which the Universe is created by bubble nucleations and contain long-range correlations in the fluctuations in the curved spacetime. The study is also relevant to the important industrial problem of designing highly curved objects, such as cars and ships, which use composite materials that contain extended correlations in their property values. We study such correlations along two- and three-dimensional curves, as well as curved surfaces. We show that such correlations are well-defined only on developable surfaces, i.e. those that can be flattened to form planar surfaces without any stretching or distortion, and preserve the distance between two points on such surfaces after the stretching. If a given curved surface is not developable, but can be approximated as piecewise developable, one may still define and analyze extended correlations on it. Representative examples are presented and analyzed.

A new model is proposed, in the context of Axelrod's model for the study of cultural dissemination, to include an external vector field (VF) which describes the effects of mass media on social systems. The VF acts over the whole system and it is characterized by two parameters: a nonnull overlap with each agent in the society and a confidence value of its information. Beyond a threshold value of the confidence, there is induced monocultural globalization of the system lined up with the VF. Below this value, the multicultural states are unstable and certain homogenization of the system is obtained in opposite line up according to that we have called negative publicity effect. Three regimes of behavior for the spread process of the VF information as a function of time are reported.

We present results on a stochastic forest fire model, where the influence of the neighbor trees is treated in a more realistic way than usual and the definition of neighborhood can be tuned by an additional parameter.

This model exhibits a surprisingly sharp phase transition which can be shifted by redefinition of neighborhood. The results can also be interpreted in terms of disease-spreading and are quite unsettling from the epidemiologist's point of view, since variation of one crucial parameter only by a few percent can result in the change from endemic to epidemic behavior.

It has been observed that a higher mutation load could be introduced into the genomes of children conceived by assisted reproduction technology (fertilization in-vitro). This generates two effects — slightly higher mutational pressure on the whole genetic pool of population and inhomogeneity of mutation distributions in the genetic pool. Computer simulations of the Penna ageing model suggest that already a small fraction of births with enhanced number of new mutations can negatively influence the whole population.

Human activities can play a crucial role in the statistical properties of observables in many complex systems such as social, technological, and economic systems. We demonstrate this by looking into the heavy-tailed distributions of observables in fatal plane and car accidents. Their origin is examined and can be understood as stochastic processes that are related to human activities. Simple mathematical models are proposed to illustrate such processes and compared with empirical results obtained from existing databanks.

Assume the initial load of an edge ij in a network to be L_ij =[(k_i ∑_{a ∈ Γi} k_a)(k_j ∑_{b ∈ Γj} k_b)]^α with k_i and k_j being the degrees of the nodes connected by the edge, where α is a tunable parameter which controls the strength of the edge initial load, and Γ_i and Γ_j are the sets of neighboring nodes of i and j, respectively. We investigate the cascading phenomenon of uncorrelated scale-free networks subject to two different attacking strategies on edges, i.e. attacking on the edges with the highest loads or the lowest loads (LL). By the critical threshold of edge capacity quantifying the network robustness, we numerically discuss the effects of two attacks for the network vulnerability. Interestingly, it is found that the attack on the edge with the LL is highly effective in disrupting the structure of the attacked network when α < 0.5. In the case of α = 0.5, the effects of two attacks for the network robustness against cascading failures are almost identical. We furthermore provide the theoretical prediction support for the numerical simulations. These results may be very helpful for real-life networks to protect the key edges selected effectively to avoid cascading-failure-induced disasters.

We have used the Monte Carlo-based computer models to show that selection pressure could affect the distribution of recombination hotspots along the chromosome. Close to the critical crossover rate, where genomes may switch between the Darwinian purifying selection or complementation of haplotypes, the distribution of recombination events and the force of selection exerted on genes affect the structure of chromosomes. The order of expression of genes and their location on chromosome may decide about the extinction or survival of competing populations.