S D Glyzin

Dimensional characteristics of diffusion chaos

The phenomenon of multimode diffusion chaos is considered. For a number of examples, it is shown by an extended numerical experiment that the Lyapunov dimension of the attractor of a distributed evolutionary dynamic system increases when the diffusion coefficient tends to zero.

Waves interaction in the Fisher–Kolmogorov equation with arguments deviation

We considered the process of density wave propagation in the logistic equation with diffusion, such as Fisher–Kolmogorov equation, and arguments deviation. Firstly, we studied local properties of solutions corresponding to the considered equation with periodic boundary conditions using asymptotic methods. It was shown that increasing of period makes the spatial structure of stable solutions more complicated. Secondly, we performed numerical analysis. In particular, we considered the problem of propagating density waves interaction in infinite interval. Numerical analysis of the propagating waves interaction process, described by this equation, was performed at the computing cluster of YarSU with the usage of the parallel computing technology—OpenMP. Computations showed that a complex spatially inhomogeneous structure occurring in the interaction of waves can be explained by properties of the corresponding periodic boundary value problem solutions by increasing the spatial variable changes interval. Thus, the complication of the wave structure in this problem is associated with its space extension.

Spatially inhomogeneous modes of logistic differential equation with delay and small diffusion in a flat area

In the paper we consider the problem of searching for coexisting modes in a nonlinear boundary value problem with a delay from population dynamics. For this we construct the asymptotic of spatially homogeneous cycle using the normal forms method and research the dependence of its stability on the diffusion parameter. Then we find coexisting attractors of the problem using numerical methods. Numerical experiment required an application of massively parallel computing systems and adaptation of solutions search algorithms to them. Based on the numerical analysis we come to the conclusion of the existence in the boundary value problem of solutions of two types. The first type has a simple spatial distribution and inherits the properties of a homogeneous solution. The second called the mode of self-organization is more complex distributed in space and is much more preferred in terms of population dynamics.

Wave propagation in the Kolmogorov–Petrovskii–Piskunov problem with delay

The problem of density wave propagation governed by a logistic equation with delay and diffusion (Fisher–Kolmogorov–Petrovskii–Piskunov equation with delay) was studied. To analyze the qualitative behavior of solutions to this equation with periodic boundary conditions in the case of the diffusion parameter tending to zero, the normal form of the problem, i.e., the Ginzburg–Landau equation was constructed near the unit equilibrium. A numerical analysis of wave propagation showed that, for sufficiently small delays, this equation has solutions close to those of the standard Kolmogorov–Petrovskii–Piskunov equation. As the delay parameter increases, a decaying oscillatory component appears in the spatial distribution of the solution and, then, undamped (in time) and slowly propagating (in space) oscillations close to solutions of the corresponding boundary value problem with periodic boundary conditions are observed near the initial perturbation segment.

Dynamic properties of the Fisher–Kolmogorov–Petrovskii–Piscounov equation with the deviation of the spatial variable

We consider the problem of the density wave propagation of a logistic equation with the deviation of the spatial variable and diffusion (the Fisher–Kolmogorov equation with the deviation of the spatial variable). The Ginzburg–Landau equation was constructed in order to study the qualitative behavior of the solution near the equilibrium state. We analyzed the profile of the wave equation and found conditions for the appearance of oscillatory regimes. The numerical analysis of the wave propagation shows that, for a fairly small spatial deviation, this equation has a solution similar to that the classical Fisher–Kolmogorov equation. An increase in this spatial deviation leads to the existence of the oscillatory component in the spatial distribution of solutions. A further increase in the spatial deviation leads to the destruction of the traveling wave. This is expressed in the fact that undamped spatiotemporal fluctuations exist in a neighborhood of the initial perturbation. These fluctuations are close to the solution of the corresponding boundary value problem with periodic boundary conditions. Finally, when the spatial deviation is large enough we observe intensive spatiotemporal fluctuations in the whole area of wave propagation.

Two-Wave Interactions in the Fermi–Pasta–Ulam Model

This work is devoted to investigating the dynamic properties of the solutions to the boundaryvalue problems associated with the classic Fermi–Pasta–Ulam (FPU) system. We analyze these problems for an infinite-dimensional case where a countable number of roots of characteristic equations tend to an imaginary axis. Under these conditions, we build a special nonlinear partial differential equation that acts as a quasi-normal form, i.e., determines the dynamics of the original boundary-value problem with the initial conditions in a sufficiently small neighborhood of the equilibrium state. The modified Korteweg–deVries (KdV) equation and the Korteweg–de Vries–Burgers (KdVB) equation act as quasi-normal forms depending on the parameter values. Under some additional assumptions, we apply the renormalization procedure to the boundary-value problems obtained. This procedure leads to an infinite-dimensional system of ordinary differential equations. We describe a method for folding this system into a special boundary- value problem, which is an analog of the normal form. The main contribution of this work is investigating the interaction of the waves moving in different directions in the FPU problem by using analytical methods of nonlinear dynamics. It is shown that the mutual influence of the waves is asymptotically small, does not affect their shape, and contributes only to a shift in their speeds, which does not change over time.

Diffusion chaos in the reaction–diffusion boundary problem in the dumbbell domain

We consider a boundary problem of the reaction–diffusion type in the domain that consists of two rectangular areas connected by a bridge. The bridge width is a bifurcation parameter of the problem and is changed in such way that the measure of the domain is preserved. The conditions on chaotic oscillations emergence have been studied and the dependence of invariant characteristics of the attractor on the bridge width has been constructed. The diffusion parameter has been chosen such that, in the case of widest possible bridge (corresponding to a rectangular domain), the spatially homogeneous cycle of the problem is orbitally asymptotically stable. By decreasing the bridge width, the homogeneous cycle loses stability; then, a spatially inhomogeneous chaotic attractor emerges. For the obtained attractor, we have calculated the Lyapunov exponents and Lyapunov dimension and observed that the dimension grows as the parameter decreases, but is bounded. We have shown that the dimension growth is connected with the growing complexity of the distribution of stable solutions with respect to the space variable.

Blue sky catastrophe in systems with nonclassical relaxation oscillations

The feasibility of the well-known blue sky bifurcation in a class of three-dimensional singularly perturbed systems of ordinary differential equations with one fast and two slow variables is studied. A characteristic property of the considered systems is that so-called nonclassical relaxation oscillations occur in them. The same name is used for oscillations with slow components, which are asymptotically close to some time-discontinuous functions and a δ-like fast component. Cases when the blue sky catastrophe results in a stable relaxation cycle or a stable two-dimensional invariant torus are analyzed. The problem of the appearance of homoclinic structures is also considered.

Double-frequency oscillations of an impulse neuron equation with two delays

The dynamics of the generalized impulse neuron equation with two delays are studied. A local analysis of the loss of the stability of the nonzero equilibrium state is carried out. The phase reorganizations of the equation under study are numerically analyzed using the obtained asymptotic formulas.