Abstract:
Let Mn be the set of linear differential systems of order n⩾2 whose coefficients are continuous and bounded on the time semiaxis R+. Denote by λ1(A)⩽…⩽λn(A) the Lyapunov exponents of a system A∈Mn, by Λ(A)=(λ1(A),…,λn(A)) their spectrum, and by es(A) the exponential stability index of A (the dimension of the linear subspace of solutions with negative characteristic exponents). For a system A∈Mn and a metric space M, we consider the class En[A](M) of continuous (n×n) matrix-valued functions Q:R+×M→Rn×n satisfying the bound ‖ for all (t,\mu)\in\mathbb{R}_+\times M, where C_Q and \sigma_Q are positive constants (possibly different for each function Q), and such that the Lyapunov exponents of the system A+Q, which are functions of \mu\in M and are denoted by \lambda_1(\mu;A+Q)\leqslant\ldots\leqslant \lambda_n(\mu;A+Q), are not less than the corresponding Lyapunov exponents of the system A; i.e., \lambda_k(\mu;A+Q)\geqslant \lambda_k(A),k=\overline{1,n}, for all \mu\in M. The problem is to obtain a complete description for each n\in\mathbb{N} and each metric space M of the class of pairs \bigl(\Lambda(A),\Lambda(\cdot\,;A+Q)\bigr) composed of the spectrum \Lambda(A)\in\mathbb{R}^n of a system A\in {\mathcal M}_n and the spectrum \Lambda(\cdot\,;A+Q)\colon M\to \mathbb{R}^n of a family A+Q, where A ranges over {\mathcal M}_n and the matrix-valued function Q ranges over the class {\mathcal E}_n[A](M) for each A, i.e., of the class \Pi {\mathcal E}_n(M)=\{\bigl(\Lambda(A),\Lambda(\cdot\,;A+Q)\bigr)\,\vert\, A\in {\mathcal M}_{n},\,Q\in {\mathcal E}_n[A](M)\}. The solution of this problem is provided by the following statement: for each integer n\geqslant 2 and every metric space M, a pair \bigl(l,F(\cdot)\bigr), where l=(l_1,\ldots,l_n)\in\mathbb{R}^n and F(\cdot)=(f_1(\cdot),\ldots,f_n(\cdot))\colon M\to \mathbb{R}^n, belongs to the class \Pi {\mathcal E}_n(M) if and only if the following conditions are met: (1) l_1\leqslant \ldots \leqslant l_n, (2) f_1(\mu)\leqslant \ldots \leqslant f_n(\mu) for all \mu\in M, (3) f_i(\mu)\geqslant l_i for all i=\overline{1,n} and \mu\in M, (4) for each i=\overline{1,n}, the function f_i(\cdot)\colon M\to \mathbb{R} is bounded and, for any r\in\mathbb{R}, the preimage f_i^{-1}([r,+\infty)) of the half-interval [r,+\infty) is a G_{\delta}-set. The solution of the similar problem of describing the pairs composed of the exponential stability index \mathrm{es}(A)\in \{0,\ldots,n\} of a system A and the exponential stability index \mathrm{es}(\cdot\,;A+Q)\colon M\to \{0,\ldots,n\} of a family A+Q, i.e., the class {\mathcal I}{\mathcal E}_n(M)=\{\bigl(\mathrm{es}(A),\mathrm{es}(\cdot\,;A+Q)\bigr)\,\vert\, A\in {\mathcal M}_{n},\,Q\in {\mathcal E}_n[A](M)\}, is contained in the following statement: for any positive integer n\geqslant 2 and every metric space M, a pair \bigl(d,f(\cdot)\bigr), where d\in\{0,\ldots,n\} and f\colon M\to\{0,\ldots,n\}, belongs to the class {\mathcal I}{\mathcal E}_n(M) if and only if f(\mu)\leqslant d for all \mu\in M and, for any r\in\mathbb{R}, the preimage f^{-1}((-\infty,r]) of the half-interval (-\infty,r] is a G_{\delta}-set.
Keywords:
linear differential system, Lyapunov exponents, perturbations vanishing at infinity, Baire classes.
Citation:
E. A. Barabanov, V. V. Bykov, “Description of the linear Perron effect under parametric perturbations exponentially vanishing at infinity”, Trudy Inst. Mat. i Mekh. UrO RAN, 25, no. 4, 2019, 31–43
\Bibitem{BarByk19}
\by E.~A.~Barabanov, V.~V.~Bykov
\paper Description of the linear Perron effect under parametric perturbations exponentially vanishing at infinity
\serial Trudy Inst. Mat. i Mekh. UrO RAN
\yr 2019
\vol 25
\issue 4
\pages 31--43
\mathnet{http://mi.mathnet.ru/timm1667}
\crossref{https://doi.org/10.21538/0134-4889-2019-25-4-31-43}
\elib{https://elibrary.ru/item.asp?id=41455518}
Linking options:
https://www.mathnet.ru/eng/timm1667
https://www.mathnet.ru/eng/timm/v25/i4/p31
This publication is cited in the following 1 articles:
A. V. Ravcheev, “Description of a linear perron effect under parametric perturbations of a linear differential system with unbounded coefficients”, Differ. Equ., 57:11 (2021), 1441–1450