Improper Actions and Higher Connectivity at Innnity

Given an improper action (= cell stabilizers are innnite) of a group G on a CW-complex X , we present criteria, based on connectivity at innnity properties of the cell stabilizers under the action of G that imply connectivity at innnity properties for G. A reenement of this idea yields information on the topology at innnity of Artin groups, and it gives signiicant progress on the question of which Artin groups are duality groups.