A residual acceleration effect due to an inhomogeneity
  The perturbed Friedmann-Lemaitre-Robertson-Walker models allow many different
possibilities for the 3-manifold of the comoving spatial section of the
Universe. It used to be thought that global properties of the spatial section,
including the topology of the space, have no feedback effect on dynamics.
However, an elementary, weak-limit calculation shows that in the presence of a
density perturbation, a gravitational feedback effect that is algebraically
similar to dark energy does exist. Moreover, the effect differs between
different 3-spaces. Among the well-proportioned spaces, the effect disappears
down to third order in several cases, and down to fifth order for the Poincare
dodecahedral space S^3/I^*. The Poincare space, that which also is preferred in
many observational analyses, is better-balanced than the other spaces.
