A signed count of 2-torsion points on real Abelian varieties

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Abstract

We prove that a natural signed count of the 2-torsion points on a real, principally polarized Abelian variety A always equals to 2g, where g is the dimension of A. When A is the Jacobian of a real curve, we derive signed counts of real odd theta characteristics. These can be interpreted in terms of the extrinsic geometry of contact hyperplanes to the canonical embedding of the curve. We also formulate a conjectural generalization to arbitrary fields in terms of the A1-enumerative geometry.

Details

Original languageEnglish
Pages (from-to)305-335
Number of pages31
JournalAnnali della Scuola Normale Superiore di Pisa. Classe di Scienze. Serie V
Volume27
Issue number1
Early online date11 Mar 2024
Publication statusPublished - 25 Feb 2026
Peer-reviewedYes

External IDs

Scopus 105036879388

Keywords