Adri Olde Daalhuis, CWI, Amsterdam
Exponentially-improved asymptotic solutions of ordinary differential equations
Re-expansions are found for the optimal remainder terms in the well-known asymptotic series solutions of homogeneous linear differential equations of the second order in the neighbourhood of an irregular singularity of rank one. The re-expansions are in terms of generalized exponential integrals and have greater regions of validity than the original expansions, as well as being considerably more accurate and providing a smooth interpretation of the Stokes phenomenon. They are also of strikingly simple form. Also found are explicit asymptotic expansions for the higher coefficients of the original asymptotic solutions.