Collapse of simple harmonic universe
  In a recent paper Graham et al constructed oscillating and static universe models which are stable with respect to all classical perturbations. Here we show that such universes are quantum-mechanically unstable and can collapse by quantum tunneling to zero radius. We also present instantons describing nucleation of oscillating and static universes from nothing. 
Audrey T. Mithani, Alexander Vilenkin
hep-th gr-qc