Background on Hecke correspondences and optimal towers
Sorry, this page is not written yet.
Meanwhile, please refer to my paper ``Explicit modular towers''
(math.NT/0103107
on the arXiv) for an overview and some explicit equations, and also to
``Explicit towers of Drinfeld modular curves''
(math.NT/0005140)
for some computations in the Drinfeld case.