Closed tachyon solitons in type II string theory

Understand

Type II theories can be described as the endpoint of closed string tachyon condensation in certain orbifolds of supercritical type 0 theories.

• In this paper, we study solitons of this closed string tachyon and analyze the nature of the resulting defects in critical type II theories.
• The solitons are classified by the real K-theory groups KO of bundles associated to pairs of supercritical dimensions.
• For real codimension 4 and 8, corresponding to $KO({\bf S}^4)={\bf Z}$ and $KO({\bf S}^8)={\bf Z}$, the defects correspond to a gravitational instanton and a fundamental string, respectively.