# Higher spins on AdS$_{3}$ from the worldsheet

## TL;DR

This paper demonstrates how the worldsheet description of string theory on AdS3 reveals a higher spin sector consistent with Vasiliev theory, especially highlighting the special case at level k=1 where massless higher spins emerge.

## Contribution

It directly identifies higher spin states from the worldsheet in AdS3 string theory, confirming their structure matches Vasiliev higher spin theory and clarifying the massless spectrum at level k=1.

## Key findings

- Higher spin states form an even spin N=4 Vasiliev theory
- Massless higher spins appear only at level k=1
- Higher spin states do not become massless at other levels

## Abstract

It was recently shown that the CFT dual of string theory on ${\rm AdS}_3 \times {\rm S}^3 \times T^4$, the symmetric orbifold of $T^4$, contains a closed higher spin subsector. Via holography, this makes precise the sense in which tensionless string theory on this background contains a Vasiliev higher spin theory. In this paper we study this phenomenon directly from the worldsheet. Using the WZW description of the background with pure NS-NS flux, we identify the states that make up the leading Regge trajectory and show that they fit into the even spin ${\cal N}=4$ Vasiliev higher spin theory. We also show that these higher spin states do not become massless, except for the somewhat singular case of level $k=1$ where the theory contains a stringy tower of massless higher spin fields coming from the long string sector.