Orbifolding the Twistor String
  The D-instanton expansion of the topological B-model on the supermanifold CP(3|4) reproduces the perturbative expansion of N=4 Super Yang-Mills theory. In this paper we consider orbifolds in the fermionic directions of CP(3|4). This operation breaks the SU(4) R-symmetry group, reducing the amount of supersymmetry of the gauge theory. As specific examples we take N=1 and N=2 orbifolds and obtain the corresponding superconformal quiver theories. We discuss the D1 instanton expansion in this context and explicitly compute some amplitudes. 
S. Giombi, M. Kulaxizi, R. Ricci, D. Robles-Llana, D. Trancanelli, K.   Zoubos