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A bstract String theory with one unit of NS-NS flux on AdS 3 × S 3 × 𝕋 4 has been recently realised to be the exact dual of the symmetric orbifold of 𝕋 4. In the hybrid formalism of Berkovits, Vafa and Witten and using the free-field realisation of psu psu (1, 1|2) 1, the DDF operators of the free bosons and the free fermions of 𝕋 4 are constructed. It is shown that these DDF operators reproduce the whole spectrum of the space-time theory on the world-sheet and therefore provide a derivation of the dual spectrum from first-principles.
Kiarash Naderi (Fri,) studied this question.