On the description of surface operators in N=2* super Yang-Mills

Understand

In Ref.

• [arXiv:1005.4469], Alday and Tachikawa observed that the Nekrasov partition function of N=2 SU(2) superconformal gauge theories in the presence of fundamental surface operators can be associated to conformal blocks of a 2D CFT with affine sl(2) symmetry.
• This can be interpreted as the insertion of a fundamental surface operator changing the conformal symmetry from the Virasoro symmetry discovered in [arXiv:0906.3219] to the affine Kac-Moody symmetry.
• A natural question arises as to how such a 2D CFT description can be extended to the case of non-fundamental surface operators.