Evgeny Kubyshkin
Publications:
Kubyshkin E. P., Moriakova A. R.
Analysis of Special Cases in the Study of Bifurcations of Periodic Solutions of the Ikeda Equation
2020, Vol. 16, no. 3, pp. 437451
Abstract
This paper deals with bifurcations from the equilibrium states of periodic solutions of the
Ikeda equation, which is well known in nonlinear optics as an equation with a delayed argument,
in two special cases that have not been considered previously. Written in a characteristic time
scale, the equation contains a small parameter with a derivative, which makes it singular. Both
cases share a single mechanism of the loss of stability of equilibrium states under changes of the
parameters of the equation associated with the passage of a countable number of roots of the
characteristic equation through the imaginary axis of the complex plane, which are in this case in
certain resonant relations. It is shown that the behavior of solutions of the equation with initial
conditions from fixed neighborhoods of the studied equilibrium states in the phase space of the
equation is described by countable systems of nonlinear ordinary differential equations that have
a minimal structure and are called the normal form of the equation in the vicinity of the studied
equilibrium state. An algorithm for constructing such systems of equations is developed. These
systems of equations allow us to single out one “fast” variable and a countable number of “slow”
variables, which makes it possible to apply the averaging method to the systems of equations
obtained. Equilibrium states of the averaged system of equations of “slow” variables in the
original equation correspond to periodic solutions of the same nature of sustainability. In the
special cases under consideration, the possibility of simultaneous bifurcation from equilibrium
states of a large number of stable periodic solutions (multistability bifurcation) and evolution
of these periodic solutions to chaotic attractors with changing bifurcation parameters is shown.
One of the special cases is associated with the formation of paired equilibrium states (a stable
and an unstable one). An analysis of bifurcations in this case provides an explanation of the
formation of the “boiling points of trajectories”, when a periodic solution arises “out of nothing”
at some point in the phase space under changes of the parameters of the equation and quickly
becomes chaotic.

Kubyshkin E. P., Moriakova A. R.
Features of Bifurcations of Periodic Solutions of the Ikeda Equation
2018, Vol. 14, no. 3, pp. 301324
Abstract
We study equilibrium states and bifurcations of periodic solutions from the equilibrium
state of the Ikeda delaydifferential equation well known in nonlinear optics. This equation was
proposed as a mathematical model of a passive optical resonator in a nonlinear environment.
The equation, written in a characteristic time scale, contains a small parameter at the derivative,
which makes it singular. It is shown that the behavior of solutions of the equation with initial
conditions from the fixed neighborhood of the equilibrium state in the phase space of the equation
is described by a countable system of nonlinear ordinary differential equations. This system
of equations has a minimal structure and is called the normal form of the equation in the
neighborhood of the equilibrium state. The system of equations allows us to pick out one
“fast” and a countable number of “slow” variables and apply the averaging method to the
system obtained. It is shown that the equilibrium states of a system of averaged equations with
“slow” variables correspond to periodic solutions of the same type of stability. The possibility of
simultaneous bifurcation of a large number of stable periodic solutions(multistability bifurcation)
is shown. With further increase in the bifurcation parameter each of the periodic solutions
becomes a chaotic attractor through a series of perioddoubling bifurcations. Thus, the behavior
of the solutions of the Ikeda equation is characterized by chaotic multistability.
