Classical geometry from the tensionless string

TL;DR

This paper investigates tensionless strings in AdS3×S3×M, revealing they can probe bulk geometry, relate to twistor-like fields, and connect to JT gravity with conical defects in a reduced AdS2 setting.

Contribution

It demonstrates that tensionless strings can explore bulk geometry, relate classical string motion to twistor-like fields, and link to Schwarzian theory in a reduced AdS2 context.

Findings

Correlation functions expressed via minimal-area worldsheets in AdS3

String motion related to twistor-like free fields

Effective action resembles Schwarzian theory of JT gravity

Abstract

Tensionless string theory on $\text{AdS}_3\times\text{S}^3\times\mathcal{M}$ is explored in the limit that the strings wind the asymptotic boundary a large number of times. Although the worldsheet is usually thought to be localised to the $\text{AdS}$ boundary, we argue that the string can actually probe the bulk geometry in this limit. In particular, we show that correlation functions can be expressed in terms of a minimal-area worldsheet propagating in $\text{AdS}_3$. We then relate the classical motion of the string to the twistor-like free field description of the tensionless worldsheet theory. Finally, we consider a particular dimensional reduction of $\text{AdS}_3$ to $\text{AdS}_2$, and show that the effective action of the worldsheet formally resembles the one-dimensional Schwarzian theory of JT gravity with conical defects.