  Heterotic orbifold compactifications yield a myriad of models that reproduce
many properties of the supersymmetric extension of the standard model and
provide potential solutions to persisting problems of high energy physics, such
as the origin of the neutrino masses and the strong CP problem. However, the
details of the phenomenology in these scenarios rely on the assumption of a
stable vacuum, characterized by moduli fields. In this note, we drop this
assumption and address the problem of moduli stabilization in realistic
orbifold models. We study their qualities and their 4D effective action, and
discuss how nonperturbative effects indeed lift all bulk moduli directions. The
resulting vacua, although still unstable, are typically de Sitter and there are
generically some quasi-flat directions which can help to deal with cosmological
challenges, such as inflation.
