Special points in three-generation moduli space

We focus on some special points in the moduli space of the three-generation compactification which give rise to a four-dimensional effective Lagrangian at the compactification scale differing markedly from that found in previous studies. In particular, we consider manifolds possessing $R$ symmetries as well as manifolds arising from blowing up an alternative construction of the three-generation class. In addition to the natural matter parities found in previous models, some of these constructions offer the substantial improvements of having fewer or no mirror quarks and exact flat directions (modulo an incomplete understanding of certain singlet modes) leading to three-generation models with SO(10), SU(5), or the standard-model gauge group at the compactification scale.