Harmonic sums and the Galois group of the Mellin-KZ difference equation

Source abstract

We identify the universal Galois group of the difference equation obtained by the Mellin transform of the Knizhnik-Zamolodchikov equation with the prounipotent group associated with the transport Hopf algebra of Deligne and Terasoma studied in \cite{Markarian}. At each finite weight, we realize the Picard-Vessiot ring by finite multiple harmonic sums. We also interpret the classical Gamma-corrected projected associator as the comparison between finite and regularized asymptotic fibers in this realization.