Congruence properties of Veech groups

Gabriela Weitze
Universität des Saarlandes
Veech groups of translation surfaces are discrete subgroups of
. In the case of a special class of translation surfaces called origamis they are actually subgroups of
of finite index. Congruence subgroups of
are groups which are fully determined by their image in
for some
. We study Veech groups which are as far as possible from being a congruence group.