Small $E_8$ Instantons and Tensionless Non-critical Strings

TL;DR

This paper investigates how zero-size E8 instantons in heterotic string theory can give rise to tensionless non-critical strings, suggesting new phase transitions in six-dimensional theories.

Contribution

It proposes a mechanism where shrinking instantons produce tensionless strings, extending understanding of phase transitions in higher-dimensional string theories.

Findings

Zero-size E8 instantons lead to tensionless non-critical strings.

Tensionless strings may induce phase transitions in six-dimensional models.

T-duality helps analyze instanton behavior at zero size.

Abstract

T-duality is used to extract information on an instanton of zero size in the $E_8\times E_8$ heterotic string. We discuss the possibility of the appearance of a tensionless anti-self-dual non-critical string through an implementation of the mechanism suggested by Strominger of two coincident 5-branes. It is argued that when an instanton shrinks to zero size a tensionless non-critical string appears at the core of the instanton. It is further conjectured that appearance of tensionless strings in the spectrum leads to new phase transitions in six dimensions in much the same way as massless particles do in four dimensions.