In a previous paper we constructed higher theta series for unitary groups over function fields, and conjectured their modularity properties. Here we prove the generic modularity of the $\ell $-adic realization of higher theta series in cohomology. The proof debuts a new type of Fourier transform, occurring on the Borel–Moore homology of moduli spaces for shtuka-type objects, that we call the arithmetic Fourier transform. Another novelty in the argument is a sheaf-cycle correspondence extending the classical sheaf-function correspondence, which facilitates the deployment of sheaf-theoretic methods to analyze algebraic cycles. Although the modularity property is a statement within classical algebraic geometry, the proof relies on derived algebraic geometry, especially a nascent theory of derived Fourier analysis on derived vector bundles, which we develop.
Accepted:
Online First:
Tony Feng  1 ; Zhiwei Yun  2 ; Wei Zhang  2
Tony Feng; Zhiwei Yun; Wei Zhang. Modularity of higher theta series I: cohomology of the generic fiber. Publications Mathématiques de l'IHÉS, Online first, pp. 1-161
@unpublished{10_5802_pmihes_27,
author = {Tony Feng and Zhiwei Yun and Wei Zhang},
title = {Modularity of higher theta series {I:} cohomology of the generic fiber},
journal = {Publications Math\'ematiques de l'IH\'ES},
year = {2026},
publisher = {IHES},
doi = {10.5802/pmihes.27},
language = {en},
note = {Online first},
}
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