A unimodular transformation is a linear transformation 
for which the determinant of the matrix 
satisfies
 |
A linear transformation of the linear span of a point lattice containing the origin maps that point lattice onto itself iff its matrix in a lattice vector basis has integer entries and is unimodular.
On the extended complex plane, the linear fractional transformation
 |
is called unimodular if 
, 
, 
, and 
are integers with 
. These linear
fractional transformations form the modular
group Gamma.
