Heterotic T-fects, 6D SCFTs, and F-theory

We study the (1, 0) six-dimensional scfts living on defects of non-geometric heterotic backgrounds (t-fects) preserving a e 7 × e 8 subgroup of e 8 × e 8. these configurations can be dualized explicitly to f-theory on elliptic k3-fibered non-compact calabi-yau threefolds. we find that the majority of the resulting dual threefolds contain non-resolvable singularities. in those cases in which we can resolve the singularities we explicitly determine the scfts living on the defect. we find a form of duality in which distinct defects are described by the same ir fixed point. for instance, we find that a subclass of non-geometric defects are described by the scft arising from small heterotic instantons on ade singularities.