Closed tachyon solitons in type II string theory

TL;DR

This paper explores solitons arising from closed string tachyon condensation in type II string theories, classifying defects via KO-theory and relating them to known objects like gravitational instantons and strings.

Contribution

It introduces a classification of closed string tachyon solitons using KO-theory and connects these defects to physical objects in string theory, offering new insights into supercritical string models.

Findings

Defects classified by KO({f S}^4) and KO({f S}^8) correspond to gravitational instantons and fundamental strings.

Reinterpretation of worldsheet GLSM as a supercritical theory with tachyon condensation.

Potential applications to F-theory and matrix factorizations on singular spaces.

Abstract

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. We apply these ideas to reinterpret the worldsheet GLSM, regarded as a supercritical theory on the ambient toric space with closed tachyon condensation onto the CY hypersurface, and use it to describe charged solitons under discrete isometries. We also suggest the possible applications of supercritical strings to the physical interpretation of the matrix factorization description of F-theory on singular spaces.