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arXiv · 2605.00673

Modular Forms and Numerical Explorations of Rational Approximations to $\zeta(3)$

Cynthia Bortolotto·Lucas Oliveira
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Abstract

We revisit Beukers' modular-form proof of the irrationality of $\zeta(3)$ from the point of view of the auxiliary weight two modular form. For the Fricke group $\Gamma_0(6)^\star$, we show that Beukers' choice is not isolated: it belongs to a one-parameter affine family. These approximations have the same exponential decay as the classical Ap\'ery approximations and satisfy the same denominator-growth estimate needed in Beukers' irrationality argument. We then apply the same construction to several other genus-zero Fricke groups.

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Cynthia Bortolotto, Lucas Oliveira. 2026-05-01. Modular Forms and Numerical Explorations of Rational Approximations to $\zeta(3)$. https://arxiv.org/abs/2605.00673

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