Normalizers of congruence groups in SL2(R) and automorphisms of lattices

Shaul Zemel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We determine the normalizer in SL2(R) of several families of congruence subgroups of SL2(Z). In addition, we show how these tools can be used to evaluate the groups of automorphisms and the discriminant kernels of a large family of isotropic lattices of signature (2,1).

Original languageAmerican English
Pages (from-to)1275-1300
Number of pages26
JournalInternational Journal of Number Theory
Issue number5
StatePublished - 1 Jun 2017

Bibliographical note

Publisher Copyright:
© 2017 World Scientific Publishing Company.


  • Congruence subgroups
  • automorphisms of lattices
  • generalized Atkin-Lehner involutions
  • normalizers


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