Thraxions: towards full string models

We elucidate various aspects of the physics of thraxions, ultra-light axions arising at Klebanov-Strassler multi-throats in the compactification space of IIB superstring theory. We study the combined stabilization of Kahler moduli and thraxions, showing that under reasonable assumptions, one can solve the combined problem both in a KKLT and a LVS setup. We find that for non-minimal multi-throats, the thraxion mass squared is threetimes suppressed by the throat warp factor. However, the minimal case of a double-throat can preserve the six-times suppression as originally found. We also discuss the backreaction of a non-vanishing thraxion vacuum expectation value on the geometry, showing that it induces a breaking of the imaginary self-duality condition for 3-form fluxes. This in turn breaks the Calabi-Yau structure to a complex manifold one. Finally, we extensively search for global models which can accommodate the presence of multiple thraxions within the database of Complete Intersection Calabi-Yau orientifolds. We find that each multi-throat system holds a single thraxion. We further point out difficulties in constructing a full-fledged global model, due to the generic presence of frozen-conifold singularities in a CalabiYau orientifold. For this reason, we propose a new database of CICY orientifolds that do not have frozen conifolds but that admit thraxions.

Automated summary

We elucidate various aspects of the physics of thraxions and study their stabilization in the context of KKLT and LVS setups. We find that the mass of the thraxion is suppressed by the throat warp factor and a non-vanishing thraxion vacuum expectation value induces a breaking of the imaginary self-duality condition. Additionally, we search for global models with multiple thraxions but encounter difficulties due to frozen conifold singularities in the Calabi-Yau orientifold. Hence, we propose a new database of CICY orientifolds that can accommodate thraxions.