Helly 1923: if every d+1 of a finite collection of convex sets in ℝ^d have common point, all do. Color/fractional/topological Helly extensions. Used in computational geometry, voting theory, LP duality.
Helly 1923: if every d+1 of a finite collection of convex sets in ℝ^d have common point, all do. Color/fractional/topological Helly extensions. Used in computational geometry, voting theory, LP duality.