  The study of axion models and quantum corrections to their potential has
experienced great progress by phrasing the axion potential in terms of a 3-form
field eating up the 2-form field dual to the axion. Such reformulation of the
axion potential has been described for axion monodromy models, and for axion
potentials from non-perturbative gauge dynamics. In this paper we propose a
3-form description of the axion potentials from non-gauge D-brane instantons.
Interestingly, the required 3-form field does not arise in the underlying
geometry, but rather shows up in the KK compactification in the generalized
geometry obtained when the backreaction of the D-brane instanton is taken into
account.
