# chaos

## Nonlinear dynamics of the backward-wave oscillator as the origin of nonstationary microwave electronics

Aim. This article presents a review of the non-stationary nonlinear phenomena in backward-wave oscillators (BWO). Methods. Numerical modeling using the nonstationary (time-domain) 1-D, 2-D, and 2-D nonlinear theory of electron beam interaction with a backward electromagnetic wave in the slowly varying amplitude approximation. Results. Main results of nonstationary nonlinear theory of O-type and M-type BWO are presented.

## Synchronization of coupled generators of quasi-periodic oscillations upon destruction of invariant curve

The purpose of this study is to describe the complete picture of synchronization of two coupled generators of quasi-periodic oscillations, to classify various types of synchronization, to study features of occurrence and destruction of multi-frequency quasi-periodic oscillations. Methods. The object of the research is systems of ordinary differential equations of various dimensions. The work uses the fourth-order Runge–Kutta method to solve a system of differential equations.

## Numerical study of dynamical system generated by CABC vector field

Purpose of this study is to construct a helical vector field and analyze the dynamical system generated by it. Classic example of such field is the ABC (Arnold–Beltrami–Childress) flow, which is equations stationary solution of the dynamics of ideal incompressible fluid. The article numerically studies the structure of the phase space of a dynamical system determined by the constructed vector field under various assumptions. Methods. When constructing a dynamic system, the approach proposed for helical fields from the class of CABC (Compressible ABC) flows was used.

## Multistability and memory effects in dynamical system with cosymmetric potential

The purpose of present study is the analysis of strong multistability in a dynamical system with cosymmetry. We study the dynamics and realization of steady-states in a mechanical system with two degrees of freedom. The minimum potential energy of the system is achieved on a curve in the form of an ellipse, which gives rise to a continuum family of equilibria and strong multistability. This problem belongs to the class of dynamical systems with cosymmetry. Methods.

## Self-oscillating system generating rough hyperbolic chaos

Topic and aim. The aim of the work is design of rough chaos generator, whose attractor implements dynamics close to Anosov flow on a manifold of negative curvature, as well as constructing and analyzing mathematical model, and

conducting circuit simulation of the dynamics using the Multisim software.

Investigated models. A mathematical model is considered that is a set of ordinary differential equations of the ninth order with algebraic nonlinearity, and a circuit representing the chaos generator is designed.

## Chaotic dynamics of pendulum ring chain with vibrating suspension

Topic and aim. The aim of the work is to introduce into consideration a mechanical system that is a chain of oscillators capable of demonstrating hyperbolic chaos due to the presence of attractor in the form of the Smale–Williams solenoid. Investigated model. We study the pendulum ring chain with parametric excitation due to the vertical oscillating motion of the suspension alternately at two diﬀerent frequencies, so that the standing wave patterns appear in the chain with a spatial scale that diﬀers by three times.

## Bifurcations and transitions to chaos in superlattice coupled to external resonator

In this letter we study nonlinear dynamics and transition to chaos in semiconductor superlattice coupled to external linear resonator. We have shown that such system demonstrates chaotic dynamics in wide range of supply voltage, whereas in autonomous superlattice only periodical dynamics exists. Revealed that transition to chaos in system goes through intermittency

## Autonomous system generating hyperbolic chaos: circuit simulation and experiment

We consider an electronic device, which represents an autonomous dynamical system with hyperbolic attractor of the Smale–Williams type in the Poincare map. Simulation of chaotic dynamics in the software environment Multisim has been undertaken. The generator of hyperbolic chaos is implemented as a laboratory model; its experimental investigation is carried out, and good compliance with the observed dynamics in the numerical and circuit simulation has been demonstrated.

## Radiative processes, radiation instability and chaos in the radiation formed by relativistic beams moving in three-dimensional (two-dimensional) space-periodic structures (natural and photonic crystals)

We review the results of studies of spontaneous and stimulated emission of relativistic particles in natural and photonic crystals. We consider the diffraction of electromagnetic waves in a crystal, and the resonance and parametric (quasi-Cherenkov) X-ray radiation, the radiation in the channeling of relativistic particles in crystals, diffraction radiation in conditions of channeling, diffraction radiation of a relativistic oscillator, induced radiation in multidimensional space-periodic resonators (natural or artificial (electromagnetic, photonic) crystals).

## Two lectures about the two ways of symmetry investigation

These lectures were delivered to the high school students at the School – seminar «Nonlinear Days for Youth in Saratov – 2012» in October 2012. They present the two ways of historical investigation of symmetry. The first way is self-similarity, i.e. invariance at dimension scale changing. In a more general way the term «scaling» is used, meaning the existence of power-law correlation between some variable and variables x1, ...xn: y = Ax_{1}^{α1}...x_{n}^{αn}, where A, α_{1},...α_{n} – are constant.