nLab Sugimoto string

Idea

A non-anomalous tachyon-free non-supersymmetric string theory obtained from an orientifold projection of the Type IIB string.

First described in Sugimoto (1999), this string theory can be obtained from introducing an orientifold plane $O9^+$ along with 32 $\overline{D9}$ anti D-branes. The resulting theory has the $USp(32)$ compact symplectic group as a gauge group. This is in contrast with the Type I string, which can be obtained from a $O9^-$ plane and 32 $D9$ branes, with a gauge group $SO(32)$.

References

The orientifold projection leading to this string was first described in:

• Shigeki Sugimoto. Anomaly cancellations in type I D-9 - anti-D-9 system and the USp(32) string theory. Prog. Theor. Phys. 102 (1999) 685-699 [hep-th/9905159, doi:10.1143/PTP.102.685]