Tensionless Strings from Worldsheet Symmetries

TL;DR

This paper explores the tensionless limit of closed bosonic string theory, revealing new degrees of freedom, connections to high-temperature string physics, and the emergence of Galilean conformal symmetry on the worldsheet.

Contribution

It introduces a covariant formulation of tensionless strings based on Galilean conformal symmetry and links tensionless and tensile vacua via Bogoliubov transformations, offering insights into high-temperature string behavior.

Findings

Tensionless strings exhibit different degrees of freedom from usual strings.

Tensionless vacuum relates to tensile vacuum through Bogoliubov transformation.

Tensionless closed strings behave like open strings.

Abstract

We revisit the construction of the tensionless limit of closed bosonic string theory in the covariant formulation in the light of Galilean conformal symmetry that rises as the residual gauge symmetry on the tensionless worldsheet. We relate the analysis of the fundamentally tensionless theory to the tensionless limit that is viewed as a contraction of worldsheet coordinates. Analysis of the quantum regime uncovers interesting physics. The degrees of freedom that appear in the tensionless string are fundamentally different from the usual string states. Through a Bogoliubov transformation on the worldsheet, we link the tensionless vacuum to the usual tensile vacuum. As an application, we show that our analysis can be used to understand physics of strings at very high temperatures and propose that these new degrees of freedom are naturally connected with the long-string picture of the Hagedorn phase of free string theory. We also show that tensionless closed strings behave like open strings.