On fundamental groups related to degeneratable surfaces: conjectures and examples
arXiv:1106.5636
Abstract
We argue that for a smooth surface S, considered as a ramified cover over the projective plane branched over a nodal-cuspidal curve B one could use the structure of the fundamental group of the complement of the branch curve to understand other properties of the surface and its degeneration and vice-versa. In this paper, we look at embedded-degeneratable surfaces - a class of surfaces admitting a planar degeneration with a few combinatorial conditions imposed on its degeneration. We close a conjecture of Teicher on the virtual solvability of the mentioned fundamental group for these surfaces and present two new conjectures on the structure of this group, regarding non-embedded-degeneratable surfaces. We prove two theorems supporting our conjectures, and show that for an empbedding of a product of a projective line with a curve of genus g, the fundamental group of the complement of the branch curve is a quotient of an Artin group associated to the degeneration.
accepted for publication at Annali della Scuola Normale Superiore