Equivariant K-theory and refined Vafa-Witten invariants

Fuente: arXiv
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Auteur principal: Thomas, Richard P.
Format: Preprint
Publié: 2018
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_version_ 1866913274950320128
author Thomas, Richard P.
author_facet Thomas, Richard P.
contents In [MT2] the Vafa-Witten theory of complex projective surfaces is lifted to oriented $\mathbb C^*$-equivariant cohomology theories. Here we study the K-theoretic refinement. It gives rational functions in $t^{1/2}$ invariant under $t^{1/2}\leftrightarrow t^{-1/2}$ which specialise to numerical Vafa-Witten invariants at $t=1$. On the "instanton branch" the invariants give the virtual $χ_{-t}^{}$-genus refinement of Göttsche-Kool. Applying modularity to their calculations gives predictions for the contribution of the "monopole branch". We calculate some cases and find perfect agreement. We also do calculations on K3 surfaces, finding Jacobi forms refining the usual modular forms, proving a conjecture of Göttsche-Kool. We determine the K-theoretic virtual classes of degeneracy loci using Eagon-Northcott complexes, and show they calculate refined Vafa-Witten invariants. Using this Laarakker [Laa] proves universality results for the invariants.
format Preprint
id arxiv_https___arxiv_org_abs_1810_00078
institution arXiv
publishDate 2018
record_format arxiv
spellingShingle Equivariant K-theory and refined Vafa-Witten invariants
Thomas, Richard P.
Algebraic Geometry
High Energy Physics - Theory
14N35
In [MT2] the Vafa-Witten theory of complex projective surfaces is lifted to oriented $\mathbb C^*$-equivariant cohomology theories. Here we study the K-theoretic refinement. It gives rational functions in $t^{1/2}$ invariant under $t^{1/2}\leftrightarrow t^{-1/2}$ which specialise to numerical Vafa-Witten invariants at $t=1$. On the "instanton branch" the invariants give the virtual $χ_{-t}^{}$-genus refinement of Göttsche-Kool. Applying modularity to their calculations gives predictions for the contribution of the "monopole branch". We calculate some cases and find perfect agreement. We also do calculations on K3 surfaces, finding Jacobi forms refining the usual modular forms, proving a conjecture of Göttsche-Kool. We determine the K-theoretic virtual classes of degeneracy loci using Eagon-Northcott complexes, and show they calculate refined Vafa-Witten invariants. Using this Laarakker [Laa] proves universality results for the invariants.
title Equivariant K-theory and refined Vafa-Witten invariants
topic Algebraic Geometry
High Energy Physics - Theory
14N35
url https://arxiv.org/abs/1810.00078