Videos

Hot Topics: Artin Groups and Arrangements - Topology, Geometry, and Combinatorics: "Towards a combinatorial characterization of K(π, 1) arrangements"

Presenter
March 12, 2024
Keywords:
  • Artin groups
  • braid groups
  • Coxeter groups
  • reflection groups
  • Garside structures
  • classifying spaces
  • hyperplane arrangements
  • subspace arrangements
  • configuration spaces
  • geometric group theory
  • Matroids
MSC:
  • 14N20
  • 20F36
Abstract
A system of half-spaces is an assignment of a half-space to each hyperplane of a real hyperplane arrangement. Such a system is said to be consistent if the intersection of the half spaces is nonempty (a chamber). Given a locally consistent system of half-spaces, using the Salvetti complex, one can construct an embedded sphere in the complexified complement. As a main result, we will show that if the system is (globally) inconsistent, then the resulting sphere gives a non-trivial element in the homotopy group, in particular, it is on-$K(\pi, 1)$ arrangement. This construction recovers many known non-$K(\pi, 1)$ arrangements. We also formulate a conjectural characterization of $K(\pi, 1)$ arrangements. K(\pi, 1)$ arrangements. We also formulate a conjectural characterization of $K(\pi, 1)$ arrangements.