Somoza's endomorphism-ring conjecture for a cyclic plane quintic

Let CC be the smooth plane curve

C:y5=x424x3+3x2+x.C:y^5=x^4-24x^3+3x^2+x.

Let JJ be its Jacobian, let K=Q(ζ9)+(ζ5)K=\mathbb{Q}(\zeta_9)^+(\zeta_5), and let OK\mathcal{O}_K denote the ring of integers of KK. Somoza's endomorphism-ring conjecture. The Jacobian JJ satisfies

End(JQ)OK.\operatorname{End}(J_{\overline{\mathbb{Q}}})\cong\mathcal{O}_K.

This conjecture predicts complex multiplication by the full ring of integers of the indicated number field for the Jacobian of Somoza's cyclic plane quintic. The supplied text gives no evidence of a resolution.

Sources & referencesView supporting material

Primary source

Marco Streng, “Explicit supersingular cyclic curves”, arXiv:2501.14902 (2025).

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