[NTNU Number Theory Seminar] Imaginary quadratic class number relations in positive characteristic

Fu-Tsun Wei observed that the sequence $\{\sigma(a)\}, a\in A$ in this context leads to a generating function on non-archimedean upper-half plane, which is a quasi-automorphic form of GL_2. over $k$, just as in the classical story. The Fourier coefficients here can also be interpreted geometrically as the intersection numbers of Hecke correspondence on product of two copies of Drinfeld curves. We shall explain this perspective.