Quantum geometry from the toroidal block Amir-Kian Kashani-Poor and Jan Troost

Abstract: We continue our study of the semi-classical (large central charge) expansion of the toroidal one-point conformal block in the context of the 2d/4d correspondence. We demonstrate that the Seiberg-Witten curve and (1-deformed) differential emerge naturally in conformal field theory when computing the block via null vector decoupling equations. This framework permits us to derive 1-deformations of the conventional relations governing the prepotential. These enable us to complete the proof of the quasi-modularity of the coefficients of the conformal block in an expansion around large exchanged conformal dimension. We furthermore derive these relations from the semi-classics of exact conformal field theory quantities, such as braiding matrices and the S-move kernel. In the course of our study, we present a new proof of Matone’s relation for N = 2 ∗ theory. 1Unite ́ Mixte du CNRS et de l’Ecole Normale Supérieure associée a ̀ l’Universite ́ Pierre et Marie Curie 6, UMR 8549. a