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The 3-cuspidal quartic and braid monodromy of degree 4 coverings. (English) Zbl 1110.14037

Ciliberto, C. (ed.) et al., Projective varieties with unexpected properties. A volume in memory of Giuseppe Veronese. Proceedings of the international conference “Varieties with unexpected properties”, Siena, Italy, June 8–13, 2004. Berlin: Walter de Gruyter (ISBN 3-11-018160-6/hbk). 113-129 (2005).
The authors study certain deformations of bidouble Galois covers of the product of two complex projective lines in connection with examples of simply connected algebraic surfaces which are diffeomorphic but not deformation equivalent. The discriminant surface of the deformation space is shown to be a quartic hypersurface isomorphic to the discriminant of the space of degree three polynomials on the projective line. Several nice properties of this hypersurface are established. The local braid monodromy of the deformed degree four coverings is determined. The local deformed branch curves that appear are the classical three-cuspidal plane quartics with a bitangent at infinity.
For the entire collection see [Zbl 1089.14001].

MSC:

14J80 Topology of surfaces (Donaldson polynomials, Seiberg-Witten invariants)
14N25 Varieties of low degree
57M12 Low-dimensional topology of special (e.g., branched) coverings
58K15 Topological properties of mappings on manifolds
32S50 Topological aspects of complex singularities: Lefschetz theorems, topological classification, invariants
14E20 Coverings in algebraic geometry