String theory axions appear to be promising candidates for explaining
cosmological constant via quintessence. In this paper, we study conditions on
the string compactifications under which axion quintessence can happen. For
sufficiently large number of axions, cosmological constant can be accounted for
as the potential energy of axions that have not yet relaxed to their minima. In
compactifications that incorporate unified models of particle physics, the
height of the axion potential can naturally fall close to the observed value of
cosmological constant.Comment: 22 page
