abstract: I will present an explicit formula for the map taking the residue at infinity of the simplest irregular connection on the Riemann sphere to the corresponding Stokes factors. The answer is expressed as a universal Lie series whose coefficients are multilogarithms. The Taylor series of the inverse (irregular Riemann-Hilbert) map is given by a similar Lie series whose coefficient are sums of products of multilogarithms labelled by rooted trees.
This is joint work with Tom Bridgeland (arXiv:0801.3974)