Isometrisable group actions
  Given a separable metrisable space X, and a group G of homeomorphisms of X, we introduce a topological property of the action of G on X which is equivalent to the existence of a G-invariant compatible metric on X. This extends a result of Marjanovic obtained under the additional assumption that X is locally compact. 
Ita\"i Ben Yaacov (ICJ), Julien Melleray (ICJ)
math.LO math.DS