The desingularization of the theta divisor of a cubic threefold as a moduli space

Arend Bayer, Sjoerd Beentjes, Soheyla Feyzbakhsh, Georg Hein, Diletta Martinelli, Fatemeh Rezaee, Benjamin Schmidt

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We show that the moduli space M¯¯¯¯¯X(v) of Gieseker stable sheaves on a smooth cubic threefold X with Chern character v=(3,−H,−H2/2,H3/6) is smooth and of dimension four. Moreover, the Abel-Jacobi map to the intermediate Jacobian of X maps it birationally onto the theta divisor Θ, contracting only a copy of X⊂M¯¯¯¯¯X(v) to the singular point 0∈Θ.
We use this result to give a new proof of a categorical version of the Torelli theorem for cubic threefolds, which says that X can be recovered from its Kuznetsov component Ku(X)⊂Db(X). Similarly, this leads to a new proof of the description of the singularity of the theta divisor, and thus of the classical Torelli theorem for cubic threefolds, i.e., that X can be recovered from its intermediate Jacobian.
Original languageEnglish
Pages (from-to)127-160
JournalGeometry & Topology
Volume28
DOIs
Publication statusPublished - 27 Feb 2024

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