On the Hecke Algebra of a Noncongruence Subgroup

Abstract

Let Γ⊂SL2(Z) be a subgroup of finite index, and let H denote the Hecke algebra of Γ. The aim of this note is to give some information about the action of H on spaces of modular forms for certain noncongruence subgroups Γ, which can be deduced from the geometric results of [9]. 1991 Mathematics Subject Classification 11F11, 11G18.