The center of small quantum groups I: the principal block in type A

We develop an elementary algebraic method to compute the center of the principal block of a small quantum group associated with a complex semisimple Lie algebra at a root of unity. The exemplary case of sl_3 is computed explicitly, and further evidence of sl_4 is sketched. This allows us to formulate the conjecture that, as a bigraded vector space, the center of a regular block of the small quantum sl_m at a root of unity is isomorphic to Haiman's diagonal coinvariant algebra for the symmetric group S_m