The Possibility of Cosmic Acceleration via Spatial Averaging in   Lemaitre-Tolman-Bondi Models
  We investigate the possible occurrence of a positive cosmic acceleration in a spatially averaged, expanding, unbound Lemaitre-Tolman-Bondi cosmology. By studying an approximation in which the contribution of three-curvature dominates over the matter density, we construct numerical models which exhibit acceleration. 
Aseem Paranjape and T. P. Singh (TIFR, Mumbai)