Normalizers of the Congruence Subgroups of the Hecke Group G5

Let$\lambda =2\cos (\pi /5)$and let G be the Hecke group associated to λ . In this article, we show that for τ a prime ideal in Z[λ], the congruence subgroups G0(τ) of G are self-normalized in PSL2( R).

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Bibliographic Details
Published in:Proceedings of the American Mathematical Society 1999-11, Vol.127 (11), p.3131-3140
Main Authors: Lang, Mong-Lung, Tan, Ser-Peow
Format: Article
Language:English
Subjects:
Mathematical congruence
Mathematical cusps
Mathematical theorems
Online Access:Get full text
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Description
Summary:Let$\lambda =2\cos (\pi /5)$and let G be the Hecke group associated to λ . In this article, we show that for τ a prime ideal in Z[λ], the congruence subgroups G0(τ) of G are self-normalized in PSL2( R).
ISSN:0002-9939
1088-6826
DOI:10.1090/s0002-9939-99-05154-0