Institution: | a CMAF-UL and Department of Mathematics, Instituto Superior Técnico Av. Rovisco Pais, 1096, Lisboa Codex, Portugal b Centro de Matemática do Porto, Praça Gomes Teixeira, P-4000, PORTO, Portugal c U.P.R. 175 CNRS Université Pierre et Marie Curie (Paris VI), 4, Place Jussieu, F-75252, Paris Cedex 05, France |
Abstract: | In this paper, a configuration with n = (2d) points in the plane is described. This configuration, as a matroid, is a Desargues configuration if d = 5, and the union of (5d) such configurations if d> 5. As an oriented matroid, it is a rank 3 truncation of the directed complete graph on d vertices. From this fact, it follows from a version of the Lefschetz-Zariski theorem implied by results of Salvetti that the fundamental group π of the complexification of its line arrangement is Artin's pure (or coloured) braid group on d strands. In this paper we obtain, by using techniques introduced by Salvetti, a new algorithm for finding a presentation of π based on this particular configuration. |