Computing with subgroups of the modular group - Kirschmer, Markus; LEEDHAM-GREEN, CHARLES (Glasgow Mathematical Journal, 2014)
We exhibit a practical algorithm for solving the constructive membership problem for discrete free subgroups of rank 2 in PSL₂(R) or SL₂(R). This algorithm, together with methods for checking whether a two-generator subgroup of PSL₂(R) or SL₂(R) is discrete and free, have been implemented in Magma for groups defined over real algebraic number fields.
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Keywords: article; General Mathematics