Heterotic NS5-branes from closed string tachyon condensation

Understand

We show how to construct the familiar heterotic NS5 brane as a topological soliton in a supercritical version of heterotic string theory.

• Closed string tachyon condensation removes the extra dimensions, leaving the NS5 in 10d, in a process highly reminiscent of the K-theoretical description of type II D-branes, but linking non-trivial gauge bundles and geometry.
• The construction requires a modification of the anomalous Bianchi identity for $H_3$ in supercritical heterotic string theory.
• We give various proofs for the existence of this modification.