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Congruence testing for odd subgroups of the modular group

Published online by Cambridge University Press:  01 May 2014

Thomas Hamilton
Affiliation:
Premier Pensions Management Corinthian House 17 Lansdowne Road Croydon CR0 2BXUnited Kingdom
David Loeffler
Affiliation:
Mathematics Institute University of Warwick Coventry CV4 7ALUnited Kingdom email d.a.loeffler@warwick.ac.uk

Abstract

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We give a computationally effective criterion for determining whether a finite-index subgroup of $\mathrm{SL}_2(\mathbf{Z})$ is a congruence subgroup, extending earlier work of Hsu for subgroups of $\mathrm{PSL}_2(\mathbf{Z})$.

Type
Research Article
Copyright
© The Author(s) 2014 

References

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