Weight k-2 cohomological p-newness conjecture

Let dMd\mid M with dMd\neq M, and define

Ck2,lψ,ϕ=(Ql/Zl)(3k)(ψ1ϕ).C_{k-2,l}^{\psi,\phi}=(\mathbb{Q}_l/\mathbb{Z}_l)(3-k)(\psi^{-1}\phi).

Let PNM/d\mathcal{P}_{NM/d} denote the set of prime divisors of NM/dNM/d, and let cHPNM/d1(Q,Ck2,lψ,ϕ)c^{”}\in H^1_{\mathcal{P}_{NM/d}}(\mathbb{Q},C_{k-2,l}^{\psi,\phi}) be the class constructed from the weight k2k-2 congruence. Set

S=pPMordλ(ψ(p)ϕ(p)pk2)>0.\mathcal{S}=\\{p\in\mathcal{P}_M\mid \operatorname{ord}_{\lambda'}(\psi(p)-\phi(p)p^{k-2})>0\\}.

Weight k2k-2 p-newness conjecture. The class cc^{”} is pp-new for every pSp\in\mathcal{S}. This is motivated by the expectation that the general newform Eisenstein congruence conjecture would allow the auxiliary eigenform to be chosen new, so that its associated cohomology class should be new at all relevant primes. The assertion is not proved in the source and remains open.

Sources & referencesView supporting material

Primary source

Dan Fretwell and Jenny Roberts, “Newform Eisenstein Congruences of Local Origin”, arXiv:2306.09842 (2026).

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