LAUSR

DOI: https://doi.org/10.1090/noti/1854 In a 1989 paper [13], Lerche, Vafa, and Warner studied the algebraic structure of 2-dimensional N = 2 supersymmetric conformal field theories (SCFT). I will not define a 2dimensional N = 2 SCFT, but only note that it is a type of quantum field theory—as such, involving operators on Hilbert spaces—in which the operators are associated with Riemann surfaces. The authors knew that a Calabi–Yau manifold gives rise to an N = 2 SCFT, the Riemann surfaces being traced out by the motions and interactions of closed strings, i.e., loops, inside the manifold. In such a theory, they wrote,