International Journal of Modern Physics C

A combination of replica exchange Monte Carlo sampling techniques and energy landscape paving approach is presented. This hybrid algorithm combines the features of the energy landscape paving (ELP) and replica exchange methods (REM). I have tested its performance in studying the low-energy conformations of the benchmark peptide Met-enkephalin.

Two aging models were analyzed on whether they can confirm the dauer mutation of the nematode helps to preserve the species. As a result the Penna model shows that populations with dauer larvae survive bad environmental conditions, whereas populations without it die out. In the Stauffer model, the advantage of the dauer mutation for the survival is only given under certain conditions.

In this paper we study the model of opinion dynamics with individuals on nodes of a scale-free network, introducing an opinion evolution mechanism and according to the nodes' degrees defining broad-sense-concept leaders on the network. We compare the strength of opinion influence between leaders and followers. With computer simulations of opinion dynamics, we found that the more complex is the scale-free network, the easier for leaders to make their opinion accepted by the masses.

New numerical methods of the ground state and thermodynamic properties calculations of one-dimensional Generalized Wigner crystal on disordered host-lattice are proposed. Unlike computer simulation methods (for instance, Monte Carlo) these methods bring the exact results. Another attractive feature of the proposed methods is their speed: it is possible to study the systems with length about 10⁴–10⁵ nodes even on a personal computer. This is especially important in the case of weakly disordered systems and the long-range correlations. The gapless structure of low-energy excitation and breaking long-range correlations at arbitrary small disordering are established.

Analytical approximate solutions for the nonlinear oscillators of the form are derived using the modified decomposition method. The analytical solutions of our model equations are calculated in the form of convergent series with easily computable components. Then the Laplace transformation and Padè approximant are effectively used to improve the convergence rate and accuracy of the computed series. The validity of the solutions is verified through some numerical examples. The results compare well with those obtained by the Runge–Kutta fourth-order method. The proposed scheme avoids the complexity provided by perturbation techniques.

Using the Voter and Chen version of an embedded-atom model, derived by fitting simultaneously to experimental data both the diatomic molecule and bulk platinum, we have studied the melting behavior of free, icosahedral, 54-, 55- and 56-atom platinum clusters in the molecular dynamics simulation technique. We present an atom-resolved analysis method that includes physical quantities such as the root-mean-square bond-length fluctuation and coordination number for individual atoms as functions of temperature. The effect of a central atom in the icosahedral structure to the melting process is discussed. The results show that the global minimum structures of the 54-, 55- and 56-atom Pt clusters do not melt at a specific temperature, rather, melting processes take place over a finite temperature range. The heat capacity peaks are not δ-functions, but instead remain finite. An ensemble of clusters in the melting region is a mixture of solid-like and liquid-like clusters.

This paper presents an analysis of the growth of towns in the Tel Aviv metropolis. It indicates a similarity in the variation of populations so that the population functions can be scaled and superposed one onto the other. This is a strong indication that the growth mechanism for all these towns is the same. Two different models are presented to interpret the population growth: one is an analytic model while the other is a computer simulation. In the dynamic analytic model, we introduced the concept of characteristic time. The growth has two parts: in the first, the derivative is an increasing function, the town is very attractive and there is short delay between decision to build and complete realization of the process. At this time, there is no shortage of land. However, around a specific time, the delay begins to increase and there is lack of available land. The rate of the population variation decreases until saturation. The two models give a good quantitative description.

The Sznajd model for the spread of opinions gives a good explanation of the influence among the neighbors, that is the external factor. In this paper, we add an internal factor to Sznajd model, which determines the probability of one's acceptance of other's opinion. We define this factor as social temperature, and we study the relationship between this temperature and time. We also consider the people who do not change their opinions as defenders and analyze their efforts.

This note explores the consequences of nonlinear price impact functions on price dynamics within the chartist–fundamentalist framework. Price impact functions may be nonlinear with respect to trading volume. As indicated by recent empirical studies, a given transaction may cause a large (small) price change if market depth is low (high). Simulations reveal that such a relationship may create endogenous complex price fluctuations even if the trading behavior of chartists and fundamentalists is linear.

Adaptive Network Fuzzy Inference System (ANFIS) is an artificial intelligence (AI)-based technique that proved efficient in a variety of problems such as classification, recognition and modeling of complex systems. This paper utilizes the adaptive network fuzzy inference system to model the K–P interactions. The ANFIS-based K–P model simulates the multiplicity distribution of charged pions at different high energies. The results showed very accurate fitting to the experimental data recommending it to be a good alternative to other theoretical techniques.

The consensus model of Krause and Hegselmann can be naturally extended to the case in which opinions are integer instead of real numbers. Our algorithm is much faster than the original version and thus more suitable for applications. For the case of a society in which everybody can talk to everybody else, we find that the chance to reach consensus is much higher as compared to other models; if the number of possible opinions Q≤7, in fact, consensus is always reached, which might explain the stability of political coalitions with more than three or four parties. For Q>7 the number S of surviving opinions is approximately the same, independent of the size N of the population, as long as Q<N. We considered as well the more realistic case of a society structured like a Barabási–Albert network; here the consensus threshold depends on the out-degree of the nodes and we find a simple scaling law for S, as observed for the discretized Deffuant model.

A de-Sitter gauge theory of the gravitational field is developed using a spherical symmetric Minkowski space–time as base manifold. The gravitational field is described by gauge potentials and the mathematical structure of the underlying space–time is not affected by physical events. The field equations are written and their solutions without singularities are obtained by imposing some constraints on the invariants of the model. An example of such a solution is given and its dependence on the cosmological constant is studied. A comparison with results obtained in General Relativity theory is also presented.