Chromatic Numbers and the Kneser Conjecture

As mentioned in the introduction, one of the main themes of Combinatorial Algebraic Topology is to study problems on the borderline between discrete mathematics and algebraic topology, whose solutions benefit from the interaction of the two fields. Usually, this implies constructing a topological space starting with a discrete object as an input, or, conversely, providing a discrete model for an already existing geometric or topological setting.