Topological String Blowup Equations via Stable Pairs
Abstract
The blowup equations of Huang, Sun and Wang are bilinear relations satisfied by the refined topological string partition function of a local Calabi--Yau 3-fold. We prove the blowup equations for the local Hirzebruch surfaces Totπ½βKπ½β, 0β€ββ€2, as identities of torus-equivariant symmetrized K-theoretic stable pair invariants; for β=2 the invariants are localized indices. The proof identifies the stable pair vertex sum, after division by the fibre contribution, with the equivariant Euler characteristic of (detπ±)β on the moduli space of framed rank 2 sheaves on β2. The blowup formulas of Nakajima--Yoshioka for framed sheaves then yield the unity and vanishing equations. For local β2 we obtain the blowup equations conditionally on two explicitly stated conjectures. We also state the Huang--Sun--Wang conjecture for general local Calabi--Yau 3-folds in the language of stable pairs, and formulate stable pair conjectures for the local rational elliptic surface involving the E8 lattice.
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BibTeX
@misc{zhao2026topological,
title = {{Topological String Blowup Equations via Stable Pairs}},
author = {Lutian Zhao},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.25397},
eprint = {2608.25397},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.25397},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Topological String Blowup Equations via Stable Pairs
AU - Lutian Zhao
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2608.25397
UR - https://arxiv.org/abs/2608.25397
AB - The blowup equations of Huang, Sun and Wang are bilinear relations satisfied by the refined topological string partition function of a local Calabi--Yau 3-fold. We prove the blowup equations for the local Hirzebruch surfaces Tot_π½_βK_π½_β, 0β€ββ€2, as identities of torus-equivariant symmetrized K-theoretic stable pair invariants; for β=2 the invariants are localized indices. The proof identifies the stable pair vertex sum, after division by the fibre contribution, with the equivariant Euler characteristic of (detπ±)^β on the moduli space of framed rank 2 sheaves on β^2. The blowup formulas of Nakajima--Yoshioka for framed sheaves then yield the unity and vanishing equations. For local β^2 we obtain the blowup equations conditionally on two explicitly stated conjectures. We also state the Huang--Sun--Wang conjecture for general local Calabi--Yau 3-folds in the language of stable pairs, and formulate stable pair conjectures for the local rational elliptic surface involving the E_8 lattice.
ER -