On the geodesic flow of surfaces of nonpositive curvature

2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/66165Let $S$ be a surface of nonpositive curvature of genus bigger than 1 (i.e. not the torus). We prove that any flat strip in the surface is in fact a flat cylinder. Moreover we prove that the number of homotopy classes of such flat cylinders is bounded.Dynamical SystemsOn the geodesic flow of surfaces of nonpositive curvaturetext