Abstract We investigate the interplay between the enumerative geometry of Calabi-Yau fourfolds with fluxes and the modularity of elliptic genera in four-dimensional string theories. We argue that certain contributions to the elliptic genus are given by derivatives of modular or quasi-modular forms. which may encode BPS invariants of Calabi-Yau or non-Calabi-Yau threefolds that are emb... https://www.billyjers.shop/product-category/swim/