Weight k-2 cohomological p-newness conjecture

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Let d∣Md\mid M with d≠Md\neq M, and define

Ck−2,lψ,ϕ=(Ql/Zl)(3−k)(ψ−1ϕ).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 c”∈HPNM/d1(Q,Ck−2,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 k−2k-2 congruence. Set

S=p∈PM∣ord⁡λ′(ψ(p)−ϕ(p)pk−2)>0.\mathcal{S}=\\{p\in\mathcal{P}_M\mid \operatorname{ord}_{\lambda'}(\psi(p)-\phi(p)p^{k-2})>0\\}.

Weight k−2k-2 p-newness conjecture. The class c”c^{”} is pp-new for every p∈Sp\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.

References

Primary source

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

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