Harris--Venkatesh conjecture for derived Hecke operators on weight-1 forms

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Let ff be a Hecke new cusp form of weight 11 and level NN, with adjoint Artin representation Ad⁡(ρ)\operatorname{Ad}(\rho). Let U(Ad⁡(ρ))\mathcal{U}(\operatorname{Ad}(\rho)) be its dual unit group, let Sp\mathfrak{S}_p denote the Shimura class, let Tr⁡pNp\operatorname{Tr}_p^{Np} be the indicated trace operator, and let f∗f^* be the dual newform. For primes p,ℓ≥5p,\ell\geq 5 coprime to NN, write log⁡ℓ:Fp×↠Z/ℓtZ\log_\ell:\mathbb{F}_p^\times\twoheadrightarrow\mathbb{Z}/\ell^t\mathbb{Z} for a fixed discrete logarithm, where ℓt\ell^t is the exact power of ℓ\ell dividing p−1p-1, and let Reg⁡Fp×\operatorname{Reg}_{\mathbb{F}_p^\times} be the finite-field regulator map.

Harris--Venkatesh conjecture. There are an element u∈U(Ad⁡(ρ))u\in\mathcal{U}(\operatorname{Ad}(\rho)) and a positive integer mm such that, for any primes p,ℓ≥5p,\ell\geq 5 coprime to NN,

m⋅log⁡ℓSp(Tr⁡pNp(f(z)f∗(pz)))=log⁡ℓReg⁡Fp×(u).m\cdot\log_\ell\mathfrak{S}_p\left(\operatorname{Tr}_p^{Np}\left(f(z)f^*(pz)\right)\right)=\log_\ell\operatorname{Reg}_{\mathbb{F}_p^\times}(u).

This conjecture predicts that the Shimura-class expression obtained from a weight-1 newform agrees, after a fixed integral scaling and discrete logarithm, with the reduction of a single Stark unit. The supplied text presents it as the Harris--Venkatesh conjecture away from the primes 22 and 33, but gives no resolution.

References

Primary source

Robin Zhang, “The Harris-Venkatesh conjecture for derived Hecke operators I: imaginary dihedral forms”, arXiv:2301.00570 (2023).

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