Anthropic Reasons for Non-Zero Flatness and Lambda

Abstract

In some cosmological theories with varying constants there are anthropic reasons why the expansion of the universe must not be too {\it close} to flatness or the cosmological constant too close to zero. Using exact theories which incorporate time-variations in $\alpha$ and in $G$ we show how the presence of negative spatial curvature and a positive cosmological constant play an essential role in bringing to an end variations in the scalar fields driving time change in these 'constants' during any dust-dominated era of a universe's expansion. In spatially flat universes with $\Lambda =0$ the fine structure constant grows to a value which makes the existence of atoms impossible.Comment: 7 pages, 5 figures, Corrected sign error and made necessary modifications. This version is accepted for publication in Phys.Rev.