Integrality structures in topological strings and quantum $2$-functions

Abstract

In this article, we first prove the integrality of open string BPS numbers for a class of toric Calabi-Yau manifolds named generalized conifolds, by applying the method introduced in our previous work \cite{LZ} to the explicit disk counting formula obtained in \cite{PS}. Then, motivated by the integrality structures in open topological string theory, we introduce a mathematical notion of ``quantum 2-function'' which can be viewed as the quantization of the notion of ``2-function'' introduced in \cite{SVW1}. Finally, we provide a basic example of quantum 2-function and discuss the quantization of 2-functions.