Theta correspondence and the Borisov-Gunnells relations

Fuente: arXiv
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Auteur principal: Branchereau, Romain
Format: Preprint
Publié: 2026
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author Branchereau, Romain
author_facet Branchereau, Romain
contents We consider a geometric theta correspondence from the first homology of a modular curve, to modular forms of weight $2$. Using Stevens' description of the homology, we find that this map sends modular symbols to product of weight one Eisenstein series, modular caps to weight $2$ Eisenstein series, and hyperbolic cycles to diagonal restrictions of Hilbert-Eisenstein series. We use it to revisit work of Borisov and Gunnells, and explain its connection to a theorem of Li. In particular, we give a geometric proof of certain relations between Eisenstein series.
format Preprint
id arxiv_https___arxiv_org_abs_2602_01473
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Theta correspondence and the Borisov-Gunnells relations
Branchereau, Romain
Number Theory
We consider a geometric theta correspondence from the first homology of a modular curve, to modular forms of weight $2$. Using Stevens' description of the homology, we find that this map sends modular symbols to product of weight one Eisenstein series, modular caps to weight $2$ Eisenstein series, and hyperbolic cycles to diagonal restrictions of Hilbert-Eisenstein series. We use it to revisit work of Borisov and Gunnells, and explain its connection to a theorem of Li. In particular, we give a geometric proof of certain relations between Eisenstein series.
title Theta correspondence and the Borisov-Gunnells relations
topic Number Theory
url https://arxiv.org/abs/2602.01473