First explicit reciprocity law for unitary Friedberg--Jacquet periods
Murilo Corato-Zanarella
TL;DR
The paper proves a Beilinson--Bloch--Kato-type vanishing result for motives attached to unitary group automorphic representations distinguished by unitary Friedberg--Jacquet periods, under an explicit set of hypotheses. It develops a comprehensive framework combining weight spectral sequences, derived Kudla--Rapoport cycles, and p-adic uniformization to relate automorphic periods to arithmetic cycles via a first explicit reciprocity law. The approach hinges on level-raising congruences in the unitary Friedberg--Jacquet setting and leverages a derived-integral-model formalism to control reductions modulo inert primes, culminating in a vanishing of the Bloch--Kato Selmer group $H^1_f(F,\rho_{\Pi,\lambda}(r))$ for admissible primes $\lambda$ when the Friedberg--Jacquet period is nonvanishing. These results reinforce the Beilinson--Bloch--Kato conjecture in a new unitary context and lay groundwork for unitary Iwasawa main conjectures via an explicit reciprocity law and Euler-system arguments.
Abstract
Consider a unitary group $G(\mathbb{A}_{F^+})=U_{2r}(\mathbb{A}_{F^+})$ over a CM extension $F/F^+$ with $G(\mathbb{A}_\infty)$ compact. In this article, we study the Beilinson--Bloch--Kato conjecture for motives associated to irreducible cuspidal automorphic representations $π$ of $G(\mathbb{A}_{F^+}).$ We prove that if $π$ is distinguished by the unitary Friedberg--Jacquet period, then the Bloch--Kato Selmer group (with coefficients in a favorable field) of the motive of $Π=\mathrm{BC}(π)$ vanishes.
