International Journal of Modern Physics C

A model of fluid membrane, which is not self-avoiding, such as two-dimensional spherical random surface is studied by using Monte Carlo simulation. Spherical surfaces in R³ are discretized by piecewise linear triangle. Dynamical variables are the positions X of the vertices and the triangulation g. The action of the model is sum of area energy and bending energy times bending rigidity b. The bending energy and the specific heat are measured, and the critical exponents of the phase transitions are obtained by a finite-size scaling technique. We find that our model of fluid membrane undergoes a second order phase transition.

We have made a comparative study for the empirical potential energy functions proposed and parametrized for coinacal metals, namely Cu, Ag, and Au. We have considered four different potential energy functions, and applied them to investigate the structural properties and energetics of clusters of the elements considered.

In the present study, we discuss how to build some partially entangled states of n two-state quantum systems (qubits). The optimal partially entangled state with a high degree of symmetry is considered to be useful for overcoming a shot noise limit of Ramsey spectroscopy under some decoherence. This state is invariant under permutation of any two qubits, and inversion between the ground state |0> and an excited state |1> for each qubit. We show that by using selective phase shifts in certain basis vectors and Grover's inversion about average operations, we can construct this high symmetric entangled state by (polynomial in n) ×2^n/2 successive unitary transformations that are applied on two or three qubits.

In quantum theory, the "spinless Salpeter equation", the relativistic generalization of the nonrelativistic Schrödinger equation, is used to describe both the bound states of scalar particles and the spin-averaged spectra of bound states of fermions. A numerical procedure solves the spinless Salpeter equation by approximating this eigenvalue equation by a matrix eigenvalue problem with explicitly known matrices.

We developed an efficient hybrid mode expansion method to study the maximum tunneling current as a function of the external magnetic field for a 2D large area lateral window junction. We consider the inhomogeneity in the critical current density, which is taken a piecewise constant. The natural modes of the expansion in y, are the linearized eigen-modes around a static solution which satisfies the 1D sine-Gordon equation with the critical current variation in y, and the boundary conditions determined by the overlap component of the bias current, which can be inline or overlap like. The magnetic field along with the inline component of the bias current enters as a boundary condition on the modal amplitudes. We obtain fast convergent results and for a ratio of idle to window widths of w₀/w = 4 (in units of λ_J), only two modes are needed. A simple scaling is obtained for the maximum tunneling current as we vary the idle region width. We also present the linear electromagnetic waveguide modes taking into account the variation normal to the waveguide of the critical current and the capacitance.

The tail of the distribution for the "mean cluster size" (susceptibility) at the site percolation threshold is found by Monte Carlo simulations to be exponential. Similar distributions might be expected for the market volatility, if stock price fluctuations are described by Cont–Bouchaud percolation.

To stimulate interaction and collaboration across scientific fields, we introduce a minimum set of biological criteria that theoretical models of aging should satisfy. We review results of several recent experiments that examined changes in age-specific mortality rates caused by genetic and environmental manipulation. The empirical data from these experiments is then used to test mathematical models of aging from several different disciplines, including molecular biology, reliability theory, physics, and evolutionary biology/population genetics. We find that none of the current models are consistent with all of the published experimental findings. To provide an example of how our criteria might be applied in practice, we develop a new conceptual model of aging that is consistent with our observations.

The effect of the periodic boundary condition (PBC) on the structure and energetics of nanotubes has been investigated by performing molecular-dynamics computer simulation. Calculations have been realized by using an empirical many-body potential energy function for carbon. A single-wall carbon nanotube has been considered in the simulations. It has been found that the periodic boundary condition has no effect at low temperature (1 K), however, it plays an important role even at intermediate temperature (300 K).

The critical behavior in short time dynamics for the q = 6 and 7 state Potts models in two-dimensions is investigated. It is shown that dynamic finite-size scaling exists for first-order phase transitions.

The two-dimensional Ising model in a small external magnetic field, is simulated on the Creutz cellular automaton. The values of the static critical exponents for 0.0025 ≤ h ≤ 0.025 are estimated within the framework of the finite size scaling theory. The value of the field critical exponent is in a good agreement with its theoretical value of δ = 15. The results for 0.0025 ≤ h ≤ 0.025 are compatible with Ising critical behavior for T < T_c.

This paper presents the parallelization of the NOABL program and its implementation on CRAY T3E parallel machine. The NOABL program is utilized to simulate windfield over complex terrain. This program runs on a processor grid (from 2 to 50 processors). The results obtained, show the interest of parallelizing this program and the SLOR method.

By an exact calculation of the ground states for the ±J Edwards–Anderson spin glass, one can extrapolate the ground state energy to infinite system sizes. We calculate the exact ground states for the three-dimensional spin glass with free boundaries for system sizes up to 10 and fit different finite-size functions. We cannot decide, only from the quality of the fit, which fitting function to choose. Relying on the literature values for the extrapolated energy, we find the finite-size corrections to vary as 1/L.

The genetic algorithms (GA) have been successfully applied to optimization problems in a variety of areas. In this paper, some modifications to GA are designed to study their performance and efficiency on a typical 2D system, 2D Ising spin glass. In particular, two kinds of modified GAs are compared for their searching ability (performance) and efficiency (convergence), by presenting a direct and visual criterion. Finally, some constructive comments and prospects on GA are presented.

Cellular automata are used to study two-dimensional local hawk-dove games. Both Nash and Pareto optimal concepts are used. The systems have fixed point, cyclic and chaotic-like regimes. The results differ significantly from that of the normal one.

It is shown that the parallel Bak–Sneppen model proposed by Sornette and Dornic can be used as an extinction model. Yet, to include the environmental effect, it may be better to augment it by a coherent noise rule. The resulting model simulates both the evolution and the extinction phenomena.

An efficient neural network (NN) has been designed to simulate the hadron–hadron interaction at high energy. Two cases have been considered simultaneously, the proton–proton (p–p) and the pion–proton (π-p) interactions. The neural network has been trained to produce the charged multiplicity distribution for both cases based on samples from the overlapping functions. The trained NN shows a good performance in matching the trained distributions. The NN is then used to predict the distributions that are not present in the training set and matched them effectively. The robustness of the designed NN in the presence of uncertainties, in the overlapping functions has been demonstrated.

This work presents a possible way to study the long-range interacting particles in finite-infinite (mesoscopic-macroscopic) systems with periodic boundary conditions. A symmetric lattice and their contributions over all space are used in the problem. In the present model, we assume that at long distances, the two-body attractive potential decays as a 1/r^α law. We verified that the potential in any particle converges (diverges) when the interactions are short(long)-ranged. On the other hand, forces in any particle converge rapidly in all cases. However, we adopt a nonextensive scaling and we guarantee that the potential converges anywhere.