Mordell's Pellian equation conjecture

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Let d∈N≥2d\in\mathbb{N}_{\geq 2} be squarefree, let K=Q(d)K=\mathbb{Q}(\sqrt{d}), let OK\mathcal{O}_K be the ring of algebraic integers of KK, and let ε>1\varepsilon>1 be the fundamental unit of OK\mathcal{O}_K. Set

ω={dif d≡2,3(mod4),frac1+d2if d≡1(mod4).\omega=\begin{cases}\sqrt{d}&\text{if }d\equiv 2,3\pmod 4,\\frac{1+\sqrt{d}}{2}&\text{if }d\equiv 1\pmod 4.\end{cases}

Write ε=x+yω\varepsilon=x+y\omega with x,y∈N0x,y\in\mathbb{N}_0. Mordell's Pellian equation conjecture. If d∈Pd\in\mathbb{P} and d≡3(mod4)d\equiv 3\pmod 4, then d∤yd\nmid y. The paper's abstract states that recently discovered counterexamples to Mordell's Pellian equation conjecture are discussed, so its status is refuted.

References

Primary source

Andreas Reinhart, “On counterexamples to Mordell's Pellian Equation Conjecture and the AAC-Conjecture: a non-computer based approach”, arXiv:2404.03038 (2025).

Additional references

2 papers in this index state this conjecture (2024). The statement above is taken from the most recent of them; the others are arXiv:2402.09827.

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