Anthropic Bound on the Cosmological Constant
In recent cosmological models, there is an "anthropic" upper bound on the cosmological constant $\ensuremath{\Lambda}$. It is argued here that in universes that do not recollapse, the only such bound on $\ensuremath{\Lambda}$ is that it should not be so large as to prevent the formation of gravitationally bound states. It turns out that the bound is quite large. A cosmological constant that is within 1 or 2 orders of magnitude of its upper bound would help with the missing-mass and age problems, but may be ruled out by galaxy number counts. If so, we may conclude that anthropic considerations do not explain the smallness of the cosmological constant.