Topological aspects of twofold triple systems (Q1272694)

This survey paper focuses on topological aspects of twofold triple systems as triangulations of surfaces with singularities, and studies the various types of surfaces that arise this way. It seems that an analogue of the Heawood map color theorem is still open in the case of pinched surfaces with a prescribed number of pinch points. The analogous problem of twofold quadruple systems and triangulations of 3-pseudomanifolds is also discussed.