Monday, 12 March, 2018

## Published in:

arXiv:1803.04423

The spectrum of superstrings on {\rm AdS}_3 \times {\rm S}^3 \times \mathbb{M}_4 with pure NS-NS flux is analysed for the background where the radius of the AdS space takes the minimal value (k=1). Both for \mathbb{M}_4={\rm S}^3 \times {\rm S}^1 and \mathbb{M}_4 = \mathbb{T}^4 we show that there is a special set of physical states, coming from the bottom of the spectrally flowed continuous representations, which agree in precise detail with the single particle spectrum of a free symmetric product orbifold. For the case of {\rm AdS}_3 \times {\rm S}^3 \times \mathbb{T}^4 this relies on making sense of the world-sheet theory at k=1, for which we make a concrete proposal. We also comment on the implications of this striking result.