On surface braids of index four with at most two crossings
Volume 188 / 2005
Fundamenta Mathematicae 188 (2005), 167-193
MSC: Primary {57Q45}; Secondary {57Q35}.
DOI: 10.4064/fm188-0-9
Abstract
Let be a 4-chart with at most two crossings. We show that if the closure of the surface braid obtained from \varGamma is one 2-sphere, then the sphere is a ribbon surface.
