We propose that string theory on ${ \rm AdS}_3 \times { \rm S}^3 \times { \rm S}^3 \times { \rm S}^1$ with $\textit{ two}$ units of NS-NS flux through each of the two $3$-spheres is exactly dual to the symmetric orbifold of $2$ bosons and $8$ free fermions. Here, one of the two bosons describes the compact ${ \rm S}^1$, while the other one corresponds to the radial (non-compact) direction of ${ \rm AdS}_3$. Unlike the analogous situation for ${ \rm AdS}_3 \times { \rm S}^3 \times \mathbb{ T}^4$, the description makes sense both in the NS-R as well as the hybrid formulation, and we explain the duality in both frameworks.
Categories: hep-th