Quintessence and the Swampland: The numerically controlled regime of
  moduli space
  We provide a detailed discussion of the main theoretical and phenomenological
challenges of quintessence model building in any numerically controlled regime
of the moduli space of string theory. We argue that a working quintessence
model requires a leading order non-supersymmetric (near) Minkowski vacuum with
an axionic flat direction. This axion, when lifted by subdominant
non-perturbative effects, could drive hilltop quintessence only for highly
tuned initial conditions and a very low inflationary scale. Our analysis has
two important implications. Firstly, scenarios which are in agreement with the
swampland conjectures, such as those that include runaways, or supersymmetric
AdS and Minkowski vacua, cannot give rise to phenomenologically viable
quintessence with full computational control. This raises doubts on the
validity of the swampland dS conjecture since it would imply a strong tension
between quantum gravity and observations. Secondly, if data should prefer
dynamical dark energy, axion models based on alignment mechanisms look more
promising than highly contrived hilltop scenarios.
