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Structural stability for dynamical systems on time scales

S. G. Kryzhevich

Gdansk University of Technology


https://youtu.be/f2XKU7qkrCg

Аннотация: We consider a system on a time scale
\begin{equation} x^\Delta=f(t,x), \quad x \in {\mathbb R}^n, \quad t\in {\mathbb T} \end{equation}
where the time scale $\mathbb T$ is an unbounded closed subset of $\mathbb R$.
Definition. We say that the system (1) is structurally stable if for any $\varepsilon>0$ there exists a $\delta>0$ such that for any $g(t,x):\quad |g(t,x)|<\delta, \quad |g'_x(t,x)|<\delta$ and any $t_0\in {\mathbb T}$ there is a homeomorphism $h$ of the space ${\mathbb R}^n$ such that
$$|\varphi_f(t,x_0)-\varphi_{f+g}(t,h(x_0))|<\varepsilon$$
for any $x_0\in {\mathbb R}^n$, $t\in {\mathbb T}$. Here $\varphi_f(t,x_0)$ and $\varphi_{f+g}(x_0)$ are solutions of systems (1) and
\begin{equation} x^\Delta=f(t,x)+g(t,x) \end{equation}
with initial conditions $x(t_0)=x_0$.
For systems of ordinary differential equations, conditions for global structural stability were obtained in [1], see also [2]. It was proved that a system is structurally stable if its linearizations are uniformly hyperbolic on families of segments.
We formulate and prove an analog of this statement for time scale systems. Although the result is very similar to that for ordinary differential equations, the proof for the time scale case is significantly different. We need to use specific approaches of time scale systems theory [3]. Remarkably, the classical results for structural stability of autonomous systems of ODEs, obtained by C.Robinson [4], are, in general, non-applicable for systems on time scales (even for the autonomous ones).
[1] S. Kryzhevich, V. Pliss, Structural stability of nonautonomous systems, Diff. equations, 39:10, (2003), 1395 – 1403.
[2] V. A. Pliss, Relation between various conditions of structural stability, Differents. Uravn., 17:5 (1981), 828 – 835.
[3] M. Bohner, A.A. Martynyuk, Elements of stability theory of A. M. Liapunov for dynamic equations on time scales, Nonlinear Dyn. Syst. Theory, 7:3, (2007), 225 – 251.
[4] C. Robinson, Structural stability of vector fields, Ann. of Math., 99:3, (1974), 447 – 493.

Язык доклада: английский


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