Casimir Energy Density at Planck Time: Cosmic Coincidence or Double   Solution to the Cosmological Dark Energy Problem?
  The Casimir energy density calculated for a spherical shell of radius equal to the size of the Universe projected back to the Planck time is almost equal to the present day critical density. Is it just a coincidence, or is it a solution to the `cosmic dark energy' and the `cosmic coincidence' problems? The correspondence is too close to be ignored as a coincidence, especially since this solution fits the conceptual and numerical ideas about the dark energy, and also answers why this energy is starting to dominate at the present era in the evolution of the Universe. 
C. S. Unnikrishnan (Tata Institute, Mumbai)