Lyapunov exponents for systems with unbounded coefficients

In this article we propose a generalization of the concept of Lyapunov exponents for discrete linear systems which may be used in the case of unbounded coefficients. We show some simplest properties of this generalization and apply it to define a generalization of regular system. Finally, we discuss the problem of stability by linear approximation. ^† This article was originally published with an error. This version has been corrected. Please see Corrigendum (http://dx.doi.org/10.1080/14689367.2012.756700).