I was reading the Maldacena Ooguri paper where they mention that for the string theory living on $AdS_3\times S_3 \times M_4$ (where $M_4$ is $K3$ or $T^4$), the boundary CFT is the supersymmetric sigma model whose target space is the moduli space of the Yang-Mills instantons on $M_4$ (See Page 28 1st line). I had two questions in this regard:
- How do I understand the moduli space of the instantons to be the target space of the boundary CFT?
- By Yang-Mills instanton, do the mean only the gauge field $A_{\mu}$ or they have instantonic contributions from the higher form gauge field (e.g. the Kalb Ramond field $B_{\mu \nu}$) as well in mind?
