Wohlfahrt's Theorem for the Hecke group G_5
Group Theory
2014-01-07 v1
Abstract
Let K be a subgroup of the inhomogeneous Hecke group G_5 of finite index. Suppose that the geometric level of K is r. Then K is congruence if and only if K contains the principal congruence subgroup of level 2r.
Keywords
Cite
@article{arxiv.1401.0776,
title = {Wohlfahrt's Theorem for the Hecke group G_5},
author = {Cheng Lien Lang and Mong Lung Lang},
journal= {arXiv preprint arXiv:1401.0776},
year = {2014}
}