Modular group
In mathematics, the modular group is the projective special linear group PSL (2, Z) {\textstyle \operatorname {PSL} (2,\mathbb {Z})} of 2 × 2 matrices with integer coefficients and determinant 1. The matrices A and − A are identified. The modular group acts on the upper-half of the complex plane by fractional linear transformations, and the name "modular group" comes from the relation to moduli spaces and not from modular arithmetic.
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