Vacuum Energy: "If Not Now, Then When?"

Abstract

For a flat universe presently dominated by static or dynamic vacuum energy, cosmological constant (LCDM) or quintessence (QCDM), we calculate the asymptotic collapsed mass fraction as function of the present ratio of smooth energy to matter energy $\text{rat}=(1-\text{omm})/\text{omm}$. Identifying these collapsed fractions as anthropic probabilities, we find the observed present ratio $\text{rat}\sim 2$ to be likely in LCDM, but most likely in QCDM.

Comments: revision, extension of astro-ph/0002204, with one extra figure