International Journal of Modern Physics C

A new multi-resolution scheme based on interpolating scaling function (ISF) on adaptive gridding (AG) shows promise in the first principle calculation. It is simpler than the wavelet scheme and fully implements the fast wavelet transformation. Although the scheme is similar to the AG scheme on real space, ISF can represent fields more effectively and needs less grids than the scheme of real space does. This simple and effective method provides an alternative to both real space and wavelet methods in the first principle calculation.

We report on a study of the Tehran Price Index (TEPIX) from 2001 to 2006 as an emerging market that has been affected by several political crises during the recent years, and analyze the non-Gaussian probability density function (PDF) of the log returns of the stock prices. We show that while the average of the index did not fall very much over the time period of the study, its day-to-day fluctuations strongly increased due to the crises. Using an approach based on multiplicative processes with a detrending procedure, we study the scale-dependence of the non-Gaussian PDFs, and show that the temporal dependence of their tails indicates a gradual and systematic increase in the probability of the appearance of large increments in the returns on approaching distinct critical time scales over which the TEPIX has exhibited maximum uncertainty.

A scheme for quantum state sharing (QSTS) of a one-particle state is proposed for a three-particle GHZ state utilized as a quantum channel. After the sender (Alice) makes Bell-state measurements (BM) on her particles, and the controller (Charlie) performs a computational basis measurement (CM), the recipient (Bob) only needs to carry out a unitary transformation of the classical information from the sender and the controller. Finally, the scheme is generalized to multiparty QSTS of a one-qubit state with n agents and an m-qubit state with n agents.

In this paper, a new cryptographic protocol to securely share a secret among a set of participants is presented. It is based on the use of non-reversible elementary cellular automata with rule numbers 90 and 150. The protocol is shown to be perfect and ideal.

Mortality, birth rates and retirement play a major role in demographic changes. In most cases, mortality rates decreased in the past century without noticeable decrease in fertility rates, leading to a significant increase in population growth. In many poor countries like Palestinian Territories the number of births has fallen and the life expectancy increased.

In this paper we concentrate on measuring, analyzing and extrapolating the age structure in Palestine a few decades ago into the future. A Fortran program has been designed and used for the simulation and analysis of our statistical data. This study of demographic change in Palestine has shown that Palestinians will have in future problems as the strongest age cohorts are the above-60-year olds. We therefore recommend the increase of both the retirement age and female employment.

We have studied a lattice spin model of nematic liquid crystal-polymer composite films by means of extensive Monte Carlo simulations over a distributed computing network. The Condor processing system installed on the Italian Nuclear Physics Institute computer network was used. The use of several geometries and boundary conditions allowed us to investigate a wide number of different realistic or speculative models. Many of the simulations differ only by a small number of parameters and they can be effectively performed in parallel. The results of the simulations can be analyzed globally when all the computations are completed and then for example, employed to extrapolate phase diagrams or other complex physical quantities. They provide an effective example of wide area distributed computing applications which could be also implemented in future GRID approaches.

In this paper, three methods for computing non-rotating neutron star models are discussed. The relativistic Oppenheimer–Volkoff (OV) equations of hydrostatic equilibrium are solved using (a) the well-known variable step method, (b) a method based on a modified form of the OV equations, where the thermodynamic enthalpy function is the independent variable, and (c) a new straightforward method, based on the ODEPACK Fortran package for solving systems of differential equations. We present results concerning several equations of state and conclusions concerning the applicability of each method.

We present an improved lattice Boltzmann model for high-speed compressible flows. The model is composed of a discrete-velocity model by Kataoka and Tsutahara¹⁵ and an appropriate finite-difference scheme combined with an additional dissipation term. With the dissipation term parameters in the model can be flexibly chosen so that the von Neumann stability condition is satisfied. The influence of the various model parameters on the numerical stability is analyzed and some reference values of parameter are suggested. The new scheme works for both subsonic and supersonic flows with a Mach number up to 30 (or higher), which is validated by well-known benchmark tests. Simulations on Riemann problems with very high ratios (1000:1) of pressure and density also show good accuracy and stability. Successful recovering of regular and double Mach shock reflections shows the potential application of the lattice Boltzmann model to fluid systems where non-equilibrium processes are intrinsic. The new scheme for stability can be easily extended to other lattice Boltzmann models.

We consider the random Erdös–Rényi network with enhanced clusterization and Ising spins s = ±1 at the network nodes. Mutually linked spins interact with energy J. Magnetic properties of the system that are dependent on the clustering coefficient C are investigated with the Monte Carlo heat bath algorithm. For J > 0 the Curie temperature T_c increases from 3.9 to 5.5 when C increases from almost zero to 0.18. These results deviate only slightly from the mean field theory. For J < 0 the spin-glass phase appears below T_SG; this temperature decreases with C, on the contrary to the mean field calculations. The results are interpreted in terms of social systems.

In this paper, we propose a simple betweenness-driven model to capture the dynamics of traffic routing choice behaviors. By comparing with two other models (degree-driven and cost-driven), it is shown that the cost-driven routing strategy is more complex and sensitive to traffic congestion. Another result indicates that the load distributions are determined by the connectivity distribution and route choice behaviors of the traffic network. The model thus provides useful insight for the design of traffic networks.

Financial markets can be modeled as complex systems. The Hugh quantity and different information affecting these markets is a remarked characteristic. However some of this information can be recovered by constructing a topology of the market. We develop a symbolic method in order to study relationships in the financial markets by constructing a minimal spanning tree (MST) and a hierarchical tree (HT). The method is successfully applied to the Italian financial market, detecting clusters with economic sense. This classification is helpful in portfolio construction and studying industrial networks.

A theoretical measure of the ionicity based on different mathematical concepts is presented in this research. Considering the distribution of valence electrons on each atom in a bond, we assume that the chemical properties of the atom can be expressed by means of probability. Using the introduced probability, different probabilistic models such as classical, fuzzy and information theoretical models have been employed to introduce new descriptors of bond ionicity. The ionicities were calculated for 12 heterodiatomic molecules and the bonds were classified in terms of covalency vs. ionicity. It was found that our proposed ionicity descriptors correlate well with the partial ionic character of the bonds.

Much research has shown that phyllotactic patterns can be considered as resulting from a growth process. A simple inhibition mechanism is used to generate automatically the spiral patterns and the magic Fibonacci numbers. We constrain the mechanism by introducing the requirement of the threshold energy-rate in producing primordia. With this modification, we are able to generate not only spiral but also whorled patterns. Our model can yield various possibilities of the whorled patterns observed in plants.