$\widehat{\mathfrak{sl}}(n)_N$ WZW conformal blocks from $SU(N)$ instanton partition functions on ${\mathbb {C}}^2/{\mathbb {Z}}_n$ (1912.04407v3)

Abstract: Generalizations of the AGT correspondence between 4D $\mathcal{N}=2$ $SU(2)$ supersymmetric gauge theory on ${\mathbb {C}}^2$ with $\Omega$-deformation and 2D Liouville conformal field theory include a correspondence between 4D $\mathcal{N}=2$ $SU(N)$ supersymmetric gauge theories, $N = 2, 3, \ldots$, on ${\mathbb {C}}^2/{\mathbb {Z}}n$, $n = 2, 3, \ldots$, with $\Omega$-deformation and 2D conformal field theories with $\mathcal{W}^{\, para}{N, n}$ ($n$-th parafermion $\mathcal{W}N$) symmetry and $\widehat{\mathfrak{sl}}(n)_N$ symmetry. In this work, we trivialize the factor with $\mathcal{W}^{\, para}{N, n}$ symmetry in the 4D $SU(N)$ instanton partition functions on ${\mathbb {C}}^2/{\mathbb {Z}}_n$ (by using specific choices of parameters and imposing specific conditions on the $N$-tuples of Young diagrams that label the states), and extract the 2D $\widehat{\mathfrak{sl}}(n)_N$ WZW conformal blocks, $n = 2, 3, \ldots$, $N = 1, 2, \ldots\, .$