Probable Values of the Cosmological Constant in a Holographic Theory
  We point out that for a large class of universes, holography implies that the most probable value of the cosmological constant is zero. In four spacetime dimensions, the probability distribution takes the Baum-Hawking form, $dP\sim\exp(cM_p^2/\Lambda)d\Lambda$. 
Petr Horava and Djordje Minic