Piecewise SL 2 Z Geometry

Peter Greenberg
1993 Transactions of the American Mathematical Society  
Piecewise SL2 Z geometry studies properties of the plane invariant under pl-homeomorphisms which, locally, have the form x >-» Ax + b , with A € SL2 Z, b € Q2 , and whose singular lines are rational. In this paper, invariants of polygons are obtained, relations with Pick's theorem are described, and a conjecture is posed.
doi:10.2307/2154401 fatcat:b3xqrnrkgzh6tmxkpzppwwrp2u