A particular type of summability of divergent power series,with an application to difference equations

Abstract

We define a “weak Borel‐sum” for a class of formal power series. This is a generalization of the ordinary Borel‐sum with applications in the theory of locally analytic difference equations. We explain its relation to a particular type of accelero‐sum obtained by the use of a weak acceleration operator, and briefly discuss a corresponding Stokes phenomenon. Most results of this paper are based on the quasi‐analyticity of a certain type of Borel transform.