1. Twisted sheaves and $$\mathrm {SU}(r) / {\mathbb {Z}}_{r}$$ Vafa–Witten theory
- Author
-
Martijn Kool and Yunfeng Jiang
- Subjects
Combinatorics ,Surface (mathematics) ,Mathematics::Algebraic Geometry ,Conjecture ,General Mathematics ,Prime number ,Duality (optimization) ,Twist ,Langlands dual group ,Partition function (mathematics) ,Moduli space ,Mathematics - Abstract
The $$\mathrm {SU}(r)$$ Vafa–Witten partition function, which virtually counts Higgs pairs on a projective surface S, was mathematically defined by Tanaka–Thomas. On the Langlands dual side, the first-named author recently introduced virtual counts of Higgs pairs on $$\mu _r$$ -gerbes. In this paper, we instead use Yoshioka’s moduli spaces of twisted sheaves. Using Chern character twisted by rational B-field, we give a new mathematical definition of the $$\mathrm {SU}(r) / {\mathbb {Z}}_r$$ Vafa-Witten partition function when r is prime. Our definition uses the period-index theorem of de Jong. S-duality, a concept from physics, predicts that the $$\mathrm {SU}(r)$$ and $$\mathrm {SU}(r) / {\mathbb {Z}}_r$$ partition functions are related by a modular transformation. We turn this into a mathematical conjecture, which we prove for all K3 surfaces and prime numbers r.
- Published
- 2021
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