Die Congruenzgruppen der sechsten Stufe. (Mit einer Figurentafel)
We study the endomorphism algebra of the motive attached to a non-CM elliptic modular cusp form. We prove that this algebra has a sub-algebra isomorphic to a certain crossed product algebra . The Tate conjecture predicts that is the full endomorphism algebra of the motive. We also investigate the Brauer class of . For example we show that if the nebentypus is real and is a prime that does not divide the level, then the local behaviour of at a place lying above is essentially determined...
We compute, in a unified way, the equations of all hyperelliptic modular curves. The main tool is provided by a class of modular functions introduced by Newman in 1957. The method uses the action of the hyperelliptic involution on the cusps.
We prove a microlocal version of the equidistribution theorem for Wigner distributions associated to cusp forms on . This generalizes a recent result of W. Luo and P. Sarnak who prove equidistribution on .