The ABCDEFG of Instantons and W-algebras
  For arbitrary gauge groups, we check at the one-instanton level that the Nekrasov partition function of pure N=2 super Yang-Mills is equal to the norm of a certain coherent state of the corresponding W-algebra. For non-simply-laced gauge groups, we confirm in particular that the coherent state is in the twisted sector of a simply-laced W-algebra. 
Christoph A. Keller, Noppadol Mekareeya, Jaewon Song, Yuji Tachikawa
hep-th