Non-tachyonic open descendants of the 0B string theory

TL;DR

The work addresses constructing tachyon-free open/closed descendants of the non-supersymmetric $0B$ string via crosscap constraints in lower-dimensional orbifolds. It employs exotic Klein bottle projections to remove tachyons in the four-dimensional $T^6/Z_3$ and six-dimensional $T^4/Z_2$ cases, yielding explicit, anomaly-free spectra and well-defined tadpole conditions. The 4D model features a chiral $U(8)⊗U(12)⊗U(12)$ gauge group with three fermion generations in specified representations, while the 6D model attains $G_{CP}=[U(16)⊗U(16)]^{⊗ 2}$ with a detailed massless spectrum and Green-Schwarz anomaly cancellation. Overall, the paper demonstrates the crosscap constraint as a powerful tool to obtain tachyon-free, potentially chiral vacua from non-supersymmetric string theories and expands the landscape of consistent orientifolds.

Abstract

We use the crosscap constraint to construct open descendants of the 0B string compactified on $T^6 /Z_3$ and on $T^4/Z_2$ free of tachyons both in the closed and in the open unoriented sectors. In four dimensions the construction results in a Chan-Paton gauge group $U(8)\otimes U(12)\otimes U(12)$ with three generations of chiral fermions in the representations $(\overline{8},1,\overline{12}) +(8,12,1)+(1,\overline{66},1)+(1,1,66)$.