I'll present a formula relating the r-th central derivative of an automorphic L-function for PGL_2 over a function field to the intersection of a pair of algebraic cycles. The intersection is between the Heegner-Drinfeld cycle considered by Yun-Zhang and a "Manin-Drinfeld" cycle of shtukas coming from the split torus. When the analytic rank is greater than 0, the formula implies that the intersection pairing vanishes, suggesting that these Manin-Drinfeld cycles may be torsion in the Chow group. Speaker(s): Ari Shnidman (Hebrew University)