IAS Physics Group Meeting

Abstract: I will review non-geometric string constructions, focusing on asymmetric orbifolds and in particular quasicrystalline orbifolds, which freeze moduli and yield isolated vacua (“string islands”). In the supersymmetric case (N=8,16), these exotic models enlarge the space of possible low-energy theories beyond those obtainable from geometry, thus avoiding the geometric lamppost. I will then turn to the 6D (1,1) classification of these orbifolds, where certain models with discrete theta angles give rise to violations of the lattice Weak Gravity Conjecture and the BPS completeness. I will comment on their connections to geometric models, which can emerge either within their moduli spaces or through strongly coupled transitions. Finally, in the non-supersymmetric setting, I will present novel 4D tachyon-free vacua with only a single neutral scalar, in close analogy to the 10d  O(16)×O(16) string.