On topological restrictions of the spacetime in cosmology
  In this paper we discuss the restrictions of the spacetime for the standard model of cosmology by using results of the differential topology of 3- and 4-manifolds. The smoothness of the cosmic evolution is the strongest restriction. The Poincare model (dodecaeder model), the Picard horn and the 3-torus are ruled out by the restrictions but a sum of two Poincare spheres is allowed. 
T. Asselmeyer-Maluga and J. Krol
gr-qc astro-ph.CO hep-th