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Emphatic convergence and sequential solutions of generalized linear differential equations

Publication at Faculty of Mathematics and Physics |
2011

Abstract

This contribution deals with systems of generalized linear differential equations of the form x_k(t)=\wt{x}_k+\int_a^t d[A_k(s)] x_k(s)+f_k(t)-f_k(a), t\in [a,b], k\in\N, where -\infty\less a\less b\less \infty, X is a Banach space, L(X) is the Banach space of linear bounded operators on X, \wt{x}_k\in X, A_k:[a,b] \to L(X) have bounded variations on [a,b], f_k: [a,b] \to X are regulated on [a,b] and the integrals are understood in the Kurzweil-Stieltjes sense. Our aim is to present new results on continuous dependence of solutions to generalized linear differential equations on the parameter k.

We continue our research from [G. Monteiro and M.

Tvrdý, Generalized linear differential equations in a Banach space: Continuous dependence on a parameter. Preprint, Institute of Mathematics, AS CR, Prague, 2011-1-17], where we were assuming that A_k tends uniformly to A and f_k tends uniformly to f on [a,b].

Here we are interested in the cases when these assumptions are violated. Furthermore, we introduce a notion of a sequential solution to generalized linear differential equations as the limit of solutions of a properly chosen sequence of ODEs obtained by piecewise linear approximations of functions A and f.

Theorems on the existence and uniqueness of sequential solutions are proved and a comparison of solutions and sequential solutions is given, as well. The convergence effects occurring in our contribution are, in some sense, very close to those described by Kurzweil and called by him emphatic convergence.