Extended Conformal Symmetry and Recursion Formulae for Nekrasov Partition Function

Abstract: We derive an infinite set of recursion formulae for Nekrasov instanton partition function for linear quiver U(N) supersymmetric gauge theories in 4D. They have a structure of a deformed version of W_{1+\infty} algebra which is called SH^c algebra (or degenerate double affine Hecke algebra) in the literature. The algebra contains W_N algebra with general central charge defined by a parameter \beta, which gives the $\Omega$ background in Nekrasov's analysis. Some parts of the formulae are identified with the conformal Ward identity for the conformal block function of Toda field theory.