Abstract. In this talk, I will discuss AdS3xS3xM4 backgrounds with pure NS-NS flux for M4=T4, K3 or S3xS1. I will show that the background with the lowest amount of NS-NS flux (`k=1') is dual to the large N limit of the symmetric product orbifold of M4. Showing this requires a description of string theory on AdS3xS3xM4 at k=1, where the standard RNS formalism breaks down. I will explain how the worldsheet theory can be consistently defined for k=1 by employing the hybrid formalism. The representation theory on the worldsheet for k=1 becomes far more restrictive than in the generic case, in particular all short string solutions and the continuum of long strings disappear, only the lowest energy long string solution is still allowed. I will also discuss the generalisation of the duality to higher flux, where the dual CFT can be described in terms of a Liouville theory.
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