Curves on K3 surfaces in divisibility 2

We prove a conjecture of Maulik, Pandharipande and Thomas expressing the Gromov–Witten invariants of K3 surfaces for divisibility 2 curve classes in all genera in terms of weakly holomorphic quasi-modular forms of level 2. Then we establish the holomorphic anomaly equation in divisibility 2 in all g...

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Main Authors: Younghan Bae, Tim-Henrik Buelles
Format: Article
Language:English
Published: Cambridge University Press 2021-01-01
Series:Forum of Mathematics, Sigma
Subjects:
Online Access:https://www.cambridge.org/core/product/identifier/S2050509421000062/type/journal_article
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author Younghan Bae
Tim-Henrik Buelles
author_facet Younghan Bae
Tim-Henrik Buelles
author_sort Younghan Bae
collection DOAJ
description We prove a conjecture of Maulik, Pandharipande and Thomas expressing the Gromov–Witten invariants of K3 surfaces for divisibility 2 curve classes in all genera in terms of weakly holomorphic quasi-modular forms of level 2. Then we establish the holomorphic anomaly equation in divisibility 2 in all genera. Our approach involves a refined boundary induction, relying on the top tautological group of the moduli space of smooth curves, together with a degeneration formula for the reduced virtual fundamental class with imprimitive curve classes. We use double ramification relations with target variety as a new tool to prove the initial condition. The relationship between the holomorphic anomaly equation for higher divisibility and the conjectural multiple cover formula of Oberdieck and Pandharipande is discussed in detail and illustrated with several examples.
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spelling doaj.art-b8e0d926e2394502bf86d5f6c7b49f262023-03-09T12:34:52ZengCambridge University PressForum of Mathematics, Sigma2050-50942021-01-01910.1017/fms.2021.6Curves on K3 surfaces in divisibility 2Younghan Bae0Tim-Henrik Buelles1ETH Zürich, Department of Mathematics, Zürich, Switzerland; E-mail:ETH Zürich, Department of Mathematics, Zürich, Switzerland; E-mail:We prove a conjecture of Maulik, Pandharipande and Thomas expressing the Gromov–Witten invariants of K3 surfaces for divisibility 2 curve classes in all genera in terms of weakly holomorphic quasi-modular forms of level 2. Then we establish the holomorphic anomaly equation in divisibility 2 in all genera. Our approach involves a refined boundary induction, relying on the top tautological group of the moduli space of smooth curves, together with a degeneration formula for the reduced virtual fundamental class with imprimitive curve classes. We use double ramification relations with target variety as a new tool to prove the initial condition. The relationship between the holomorphic anomaly equation for higher divisibility and the conjectural multiple cover formula of Oberdieck and Pandharipande is discussed in detail and illustrated with several examples.https://www.cambridge.org/core/product/identifier/S2050509421000062/type/journal_article14N3514J2811F03
spellingShingle Younghan Bae
Tim-Henrik Buelles
Curves on K3 surfaces in divisibility 2
Forum of Mathematics, Sigma
14N35
14J28
11F03
title Curves on K3 surfaces in divisibility 2
title_full Curves on K3 surfaces in divisibility 2
title_fullStr Curves on K3 surfaces in divisibility 2
title_full_unstemmed Curves on K3 surfaces in divisibility 2
title_short Curves on K3 surfaces in divisibility 2
title_sort curves on k3 surfaces in divisibility 2
topic 14N35
14J28
11F03
url https://www.cambridge.org/core/product/identifier/S2050509421000062/type/journal_article
work_keys_str_mv AT younghanbae curvesonk3surfacesindivisibility2
AT timhenrikbuelles curvesonk3surfacesindivisibility2