Anomaly Cancellations in the Type I D9-anti-D9 System and the USp(32) String Theory

TL;DR

This paper investigates anomaly cancellation in type I string theory involving D9-anti-D9 systems, demonstrating conditions under which gauge and gravitational anomalies cancel, leading to a tachyon-free USp(32) string theory without supersymmetry.

Contribution

It identifies anomaly cancellation conditions for D9-anti-D9 systems with USp gauge groups and shows how tachyon condensation yields a stable, non-supersymmetric USp(32) string theory.

Findings

Anomaly cancellation occurs when n-m=32 for SO(n) x SO(m) gauge groups.

USp(n) x USp(m) gauge symmetry also satisfies anomaly cancellation.

Tachyon condensation leads to a stable USp(32) string theory without spacetime supersymmetry.

Abstract

We check some consistency conditions for the D9-anti-D9 system in type I string theory. The gravitational anomaly and gauge anomaly for SO(n) x SO(m) gauge symmetry are shown to be cancelled when n-m=32. In addition, we find that a string theory with USp(n) x USp(m) gauge symmetry also satisfies the anomaly cancellation conditions. After tachyon condensation, the theory reduces to a tachyon-free USp(32) string theory, though there is no spacetime supersymmetry.