In a celebrated unpublished manuscript Beilinson and Drinfeld quantize the
Hitchin integrable system by showing that the global sections of critically
twisted differential operators on the moduli stack of G-bundles on an algebraic
curve is identified with the ring of regular functions on the space of G-opers;
they deduce existence of an automorphic D-module corresponding to a local
system carrying a structure of an oper. In this note we show for G=GL(n) that
those results admit a short proof by reduction to positive characteristic,
where the result is deduced from generic Langlands duality established earlier
by the first author and A. Braverman. The appendix contains a proof of some
properties of the p-curvature map restricted to the space of opers.Comment: paper by Roman Bezrukavnikov and Roman Travkin with an appendix by
Roman Bezrukavnikov, Tsao-Hsien Chen and Xinwen Zhu. 13 page