International Journal of Modern Physics C

One of the most important characteristics in the survival of a species is related to the kind of reproduction responsible for the offspring generation. However, only in the last years the role played by sexual reproduction has been investigated. Then, for a better understanding of this kind of process we introduce, in this work, a surface reaction model that describes the role of the sexual reproduction. In our model two different elements of the species, representing male and female, can interact to reproduce a new element. The sex of this new element is chosen with a given probability and in order to take into account the mortality rate we introduce another kind of individual. The value of the spatial density of this element remains constant during the time evolution of the system. The model is studied using Monte Carlo simulations and mean field approximation. Depending on the values of the control parameters of the model, the system can attain two stationary states: In one of them the population survives and in the other it can be extinguished. Besides, accordingly to our results, the phase diagram of the model shows a discontinuous transition between these two states.

In this paper, the interaction of shock waves with multi-fluids interfaces is investigated by numerical simulations using unstructured quadrilateral adaptive meshes. In order to obtain a detailed structure of the interface, a solution adaptive method for compressible multi-fluid flows developed by Zheng et al. is employed. Firstly, the method is verified by a planar shock and interface interaction problem, which is compared with the front tracking method for the Richtmyer–Meshkov instability problem. Following the verification, the interaction between a circular shock and a sinusoidally perturbed circular interface in cylinder vessel is firstly investigated in our paper. The results show that the solution adaptive method can be employed to study the compressible multi-fluid cases with relatively complex geometry as well as capturing the fine details of interfacial structures of the interaction.

The binary-state opinion model with the conservation law of public information is studied. The public information Inf_i provided by node i is an exponential function of its degree with the tunable parameter β, which reflects the impact factor of the node i to his/her local neighbors. We realize our model on the top of complex networks with another tunable parameter α, which shows the degree heterogeneous as the form of the power-law degree distribution with the exponent γ = (1 + α)/α. We find that much more public information (β > 2) and less public information (β < -1) cannot let either of the two opinions win during the opinion formation. In the (α,β) space, the system undergoes the doubling bifurcation and then after a point becomes chaotic when the α decreases from 1 to 0. Maybe, our present work can provide some perspectives and tools to understand the conversation of opinion formation in our society.

We perform numerical simulations of a new proposal of laboratory experiment that would allow the transformation of a classical fluid into a quantum-type (super)fluid through the application of a generalized quantum potential. This quantum potential is simulated by using a real time retroactive loop involving a measurement of density, a calculation of the potential in function of the measured density, then an application of the calculated potential through a classical force. This general experimental concept is exemplified here by the case of a nonspreading oscillating wave packet in a harmonic oscillator potential. We find signatures of a quantum-like behavior which are stable against various perturbations. Finally, the feasability of a realization of this concept in an actual plasma experiment is analyzed.

Lattice Boltzmann method (LBM) has made great progress in the last decade, and its application became wider and wider. In this paper, based on our former combustion LBM model on the macroscale, we attempt to extend it into premixed microcombustion simulation. Considering the external heat losses in microcombustion, the second-order implicit scheme for boundary condition treatment was adopted in our LBM model. Numerical tests have proved that its accuracy and stability were suitable. Furthermore, planar microcombustion with backward-facing step was also studied in order to show its different performances and improvement, which are compared with microcombustor without back step.

In this paper, we modify the Runge–Kutta–Fehlberg code of fourth and fifth order with the purpose of solving initial value problems established on ordinary differential equations involving complex-valued functions of one complex variable, which are allowed to have high complexity in their definition, when integration along prescribed complex paths is required. Such initial value problems arise in certain astrophysical issues, like the polytropic models, applied to polytropic stars, and the general-relativistic polytropic models, applied to neutron stars. Comparison with similar codes is made by applying to these models.

Different types of the lattice spin systems with the competing interactions have rich and interesting phase diagrams. In this study a system with competing nearest-neighbor interaction J₁, prolonged next-nearest-neighbor interaction J_p and ternary prolonged interaction J_tp is considered on a Cayley tree of arbitrary order k. To perform this study, an iterative scheme is developed for the corresponding Hamiltonian model. At finite temperatures several interesting properties are presented for typical values of α = T/J₁, β = −J_p/J₁ and γ = -J_tp/J₁. This study recovers as particular cases, previous work by Vannimenus¹ with γ = 0 for k = 2 and Ganikhodjaev et al.² in the presence J₁, J_p, J_tp with k = 2. The variation of the wavevector q with temperature in the modulated phase and the Lyapunov exponent associated with the trajectory of our iterative system are studied in detail.

A multiple-relaxation-time (MRT) collision operator is introduced into the author's rectangular lattice Boltzmann method for simulating fluid flows. The model retains both the advantages and the standard procedure of using a constant transformation matrix in the conventional MRT scheme on a square lattice, leading to easy implementation in the algorithm. This allows flow problems characterized by dominant feature in one direction to be solved more efficiently. Two numerical tests have been carried out and shown that the proposed model is able to capture complex flow characteristics and generate an accurate solution if an appropriate lattice ratio is used. The model is found to be more stable compared to the original rectangular lattice Boltzmann method using the single relaxation time.