
arXiv: 1203.1645
We discuss properties of complex algebraic orbifold groups, their characteristic varieties, and their abelian covers. In particular, we deal with the question of (quasi)-projectivity of orbifold groups. We also prove a structure theorem for the variety of characters of normal-crossing quasi-projective orbifold groups. Finally, we extend Sakuma's formula for the first Betti number of abelian covers of orbifold fundamental groups. Several examples are presented, including a compact orbifold group which is not projective and a Zariski pair of plane projective curves that can be told by considering an unbranched cover of the projective plane with an orbifold structure.
20 pages
14H30, 57R18, 55N25, Mathematics - Algebraic Geometry, Mathematics - Geometric Topology, FOS: Mathematics, Geometric Topology (math.GT), Algebraic Geometry (math.AG)
14H30, 57R18, 55N25, Mathematics - Algebraic Geometry, Mathematics - Geometric Topology, FOS: Mathematics, Geometric Topology (math.GT), Algebraic Geometry (math.AG)
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