2d TQFT structure of the superconformal indices with outer-automorphism   twists
  We study the superconformal indices of 4d theories coming from 6d N=(2,0) theory of type \Gamma on a Riemann surface, with the action of the outer-automorphism \sigma in the trace. We find that the indices are given by the partition function of a deformed 2d Yang-Mills on the Riemann surface with gauge group G which is S-dual to the subgroup of \Gamma fixed by \sigma. In the 2-parameter deformed version, we find that it is governed not by Macdonald polynomials of type G, but by Macdonald polynomials associated to twisted affine root systems. 
Noppadol Mekareeya, Jaewon Song and Yuji Tachikawa
hep-th