Minimal models for Hilbert modular surfaces of principal congruence subgroups

Congruence Subgroups of the Modular Group

The congruence subgroups of the classical modular group which can be defined as the automorphs modulo q of some fixed matrix are studied, and their genera determined. Let T = SL{2, Z). A congruence subgroup of T is any subgroup containing a principal congruence subgroup T^), defined as the set of elements A of T such that A = I mod q, where q is a positive integer. Of these one of the most impo...

Cuspidal Cohomology for Principal Congruence Subgroups of Gl(3, Z)

The cohomology of arithmetic groups is made up of two pieces, the cuspidal and noncuspidal parts. Within the cuspidal cohomology is a subspace— the /-cuspidal cohomology—spanned by the classes that generate representations of the associated finite Lie group which are cuspidal in the sense of finite Lie group theory. Few concrete examples of /-cuspidal cohomology have been computed geometrically...

Foliations of Hilbert modular surfaces

The Hilbert modular surface XD is the moduli space of Abelian varietiesA with real multiplication by a quadratic order of discriminant D > 1. The locus where A is a product of elliptic curves determines a finite union of algebraic curves XD(1) ⊂ XD. In this paper we show the lamination XD(1) extends to an essentially unique foliation FD of XD by complex geodesics. The geometry of FD is related ...

Tate Conjectures for Hilbert Modular Surfaces

Squares of Congruence Subgroups of the Extended Modular Group

In this paper, we generalize some results related to the congruence subgroups of modular group ; given in [7] and [6] by Kiming, Schütt, and Verrill, to the extended modular group ̆: 2010 Mathematics Subject Classification: 11F06