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

Understand

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.