Fourier-coefficient relation conjecture for Jacobi cusp forms

Let k>4k>4 with k2k\equiv 2 modulo 44. For every reduced matrix T\halfint2+T\in\halfint^+_2 with bottom-right entry mm, let Sm(n,T)S_m(n,T) be the set of integers rr such that T~=\smT\halfint2+\widetilde{T}=\smT\in\halfint^+_2 and, for j=1,,dj=1,\ldots,d, the displayed ratios of Fourier coefficients satisfy

a2k(\TdivT~tj)a2k(T~)=a2k(\TdivTtj)a2k(T).\frac{a^k_2(\Tdiv{\widetilde{T}}{t_j})}{a^k_2(\widetilde{T})}=\frac{a^k_2(\Tdiv{T}{t_j})}{a^k_2(T)}.

Here cn,rc_{n,r} denotes the corresponding functional on Jk,mcusp(Q)J_{k,m}^{\mathrm{cusp}}(\mathbb{Q}). Fourier-coefficient relation conjecture. For every such TT, there exist arbitrarily large integers AA and positive rational numbers μn,r\mu_{n,r} such that

1nArSm(n,T)μn,rcn,rJk,mcusp(Q)=0.\sum_{1\leq n\leq A}\sum_{r\in S_m(n,T)}\mu_{n,r}c_{n,r}\big|_{J_{k,m}^{\mathrm{cusp}}(\mathbb{Q})}=0.

This conjecture is presented as a refinement of an earlier lemma and is intended to imply the existence of the subcones needed for the generalization to every non-squarefree mm; the supplied excerpt does not establish it.

Sources & referencesView supporting material

Primary source

Riccardo Zuffetti, “Cones of special cycles of codimension 2 on orthogonal Shimura varieties”, arXiv:2202.12610 (2022).

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