Confluence of meromorphic solutions of q-difference equations

Thomas Dreyfus

Published 2013-07-26, updated 2015-04-15Version 2

In this paper, we consider a q-analogue of the Borel-Laplace summation where q>1 is a real parameter. In particular, we show that the Borel-Laplace summation of a divergent power series solution of a linear differential equation can be uniformly approximated on a convenient sector, by a meromorphic solution of a corresponding family of linear q-difference equations. We perform the computations for the basic hypergeometric series. Following J. Sauloy, we prove how a fundamental set of solutions of a linear differential equation can be uniformly approximated on a convenient domain by a fundamental set of solutions of a corresponding family of linear q-difference equations. This leads us to the approximations of Stokes matrices and monodromy matrices of the linear differential equation by matrices with entries that are invariants by the multiplication by q.