Sphere Packings in 3 Dimensions
  This short note describes the tentative form of a finite-dimensional optimization problem that may be of use in a second-generation proof of the Kepler conjecture. In the original 1998 proof of the Kepler conjecture, the form of the optimization problem was constrained by limits to computer power and by the speed of the algorithms that were available in 1994 to prove inequalities by computer. The computational resources have changed considerably since then, and much has been learned by an analysis of the 1998 proof. This analysis has lead to the proposed new form for an optimization problem. 
Thomas C. Hales