Mirror symmetry for singular double cover Calabi--Yau varieties: quantum test
Tsung-Ju Lee, Bong H. Lian, Shing-Tung Yau
TL;DR
The paper extends mirror symmetry to singular Calabi--Yau double covers arising from nef-partitions on semi-Fano toric manifolds, formulating a quantum mirror test between the $A$-model and the $B$-model in this singular setting. Using gauge-fixed double covers and Batyrev--Borisov duality, it constructs mirror pairs $(Y,Y^ abla)$ and analyzes their periods via GKZ $A$-hypergeometric systems, matching them to untwisted genus-zero orbifold Gromov--Witten invariants through cohomology-valued $B$-series. For two explicit branching configurations on $P^3$, the authors prove a mirror theorem: the $A$-model correlators of $Y$ coincide with the $B$-model correlators of $Y^ abla$ after a mirror map, with Gamma-factor effects playing a crucial role in normalization and instanton counts (e.g., $n_1=64$ for the first case). Morrison's conjecture is also tested in this framework, showing extremal transitions are reversed under the singular mirror correspondence and linking through dual polytopes. Overall, the work provides concrete computational evidence and a robust toolkit for quantum mirror symmetry in singular CYs within toric and GLSM-inspired contexts, enriching the dialogue between topological and geometric aspects of mirror symmetry.
Abstract
We continue our study on the pairs of singular Calabi--Yau varieties arising from double covers over semi-Fano toric manifolds. In this paper, we first investigate singular CY double covers of \(\mathbb{P}^{3}\) branched along (1) a union of eight hyperplanes in general position, and (2) a union of four hyperplanes and a quartic in generation. Our previous construction produces hypothetical singular mirror partners. We prove that they are mirror pairs in the sense that the \(B\)-model of one (variation of Hodge structure) is equivalent to the \(A\)-model of another (the untwisted part of the genus zero orbifold Gromov--Witten invariants). The technique can be generalized and applied to the case when the nef-partition is trivial. As a byproduct, we also verify Morrison's conjecture in certain circumstances.
