On the Sen limit squared

We introduce a class of F-theory vacua which may be viewed as a specialization of the so-called E6 fibration, and construct a weak coupling limit associated with such vacua which we view as the ‘square’ of the Sen limit. We find that while Sen's limit is naturally viewed as an orientifold theory, the universal tadpole relation which equates the D3 charge between the associated F-theory compactification and the limit we construct suggests that perhaps the limiting theory is in fact an oriented theory compactified on the base of the F-theory elliptic fibration.