Dark Energy, Extra Dimensions, and the Swampland
  Perhaps the greatest challenge for fundamental theories based on
compactification from extra dimensions is accommodating a period of accelerated
cosmological expansion. Previous studies have identified constraints imposed by
the existence of dark energy for two overlapping classes of compactified
theories: (1) those in which the higher dimensional picture satisfies certain
metric properties selected to reproduce known low energy phenomenology; or (2)
those derived from string theory assuming they satisfy the Swampland
conjectures. For either class, the analyses showed that dark energy is only
possible if it takes the form of quintessence. In this paper, we explore the
consequences for theories that belong to both classes and show that the joint
constraints are highly restrictive, leaving few options.
