Algebraic-rank criterion and exterior-power description of plectic Heegner classes

Let AA be the abelian variety, EE the number field, LcL_{\mathfrak c} the anticyclotomic extension, and let χ\chi be a character. Let rr be the number of primes in S\mathcal{S}, let κA,Sχ\kappa^{\chi}_{A,\mathcal{S}} be the plectic Heegner class, and write ralg(A/E,χ)r_\mathrm{alg}(A/E,\chi) for the algebraic rank. Let

det ⁣:rA(Lc)Hf1(E,S,Vp(A))Hf1(Lc,Vp(A))\operatorname{det}\colon \bigwedge^r A(L_{\mathfrak c})\longrightarrow \mathrm{H}^1_f(E_{\otimes,\mathcal{S}},V_p(A))\otimes \mathrm{H}^1_f(L_{\mathfrak c},V_p(A))

be the homomorphism defined using the chosen embeddings and the Kummer map. Algebraic-rank criterion for plectic Heegner classes. If ralg(A/E,χ)rr_\mathrm{alg}(A/E,\chi)\ge r, then

κA,Sχ0    ralg(A/E,χ)=r.\kappa^{\chi}_{A,\mathcal{S}}\ne 0\quad\iff\quad r_\mathrm{alg}(A/E,\chi)=r.

Moreover, there exists wA,SχrA(Lc)χw_{A,\mathcal{S}}^\chi\in\bigwedge^r A(L_{\mathfrak c})^\chi such that

κA,Sχ=det(wA,Sχ).\kappa^{\chi}_{A,\mathcal{S}}=\operatorname{det}\bigl(w_{A,\mathcal{S}}^\chi\bigr).

This conjecture predicts that, once the algebraic rank is at least the number of auxiliary primes, nonvanishing occurs exactly in the minimal-rank case and that the class is generated by an exterior-power element.

Sources & referencesView supporting material

Primary source

Michele Fornea, “Plectic Heegner classes”, arXiv:2603.28327 (2026).

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