Abstract
We study the problem of describing square-free polynomials \(f(x)\) of odd degree with periodic expansion of \(\sqrt{f(x)}\) into a functional continued fraction in \(k((x))\), where \(k\subseteq\overline{\mathbb Q}\). We obtain a complete description of such polynomials \(f(x)\) that does not depend on the field \(k\) and the degree of a polynomial, provided that the degree \(U\) of the fundamental \(S\)-unit of the corresponding hyperelliptic field \(k(x)(\sqrt{f(x)})\) either does not exceed \(12\) or is even and does not exceed \(20\).
References
N. H. Abel, “Ueber die Integration der Differential-Formel \(\frac {\rho dx}{\sqrt R}\), wenn \(R\) und \(\rho \) ganze Functionen sind,” J. Reine Angew. Math. 1, 185–221 (1826).
D. S. Kubert, “Universal bounds on the torsion of elliptic curves,” Proc. London Math. Soc., Ser. 3, 33 (2), 193–237 (1976).
M. M. Petrunin, “\(S\)-units and periodicity of square root in hyperelliptic fields,” Dokl. Math. 95 (3), 222–225 (2017) [transl. from Dokl. Akad. Nauk 474 (2), 155–158 (2017)].
V. P. Platonov, “Number-theoretic properties of hyperelliptic fields and the torsion problem in Jacobians of hyperelliptic curves over the rational number field,” Russ. Math. Surv. 69 (1), 1–34 (2014) [transl. from Usp. Mat. Nauk 69 (1), 3–38 (2014)].
V. P. Platonov and G. V. Fedorov, “On the problem of periodicity of continued fractions in hyperelliptic fields,” Sb. Math. 209 (4), 519–559 (2018) [transl. from Mat. Sb. 209 (4), 54–94 (2018)].
V. P. Platonov and G. V. Fedorov, “On the problem of classification of periodic continued fractions in hyperelliptic fields,” Russ. Math. Surv. 75 (4), 785–787 (2020) [transl. from Usp. Mat. Nauk 75 (4), 211–212 (2020)].
V. P. Platonov and M. M. Petrunin, “Groups of \(S\)-units and the problem of periodicity of continued fractions in hyperelliptic fields,” Proc. Steklov Inst. Math. 302, 336–357 (2018) [transl. from Tr. Mat. Inst. Steklova 302, 354–376 (2018)].
V. P. Platonov and M. M. Petrunin, “On the finiteness of the number of expansions into a continued fraction of \(\sqrt {f}\) for cubic polynomials over algebraic number fields,” Dokl. Math. 102 (3), 487–492 (2020) [transl. from Dokl. Ross. Akad. Nauk, Mat. Inform. Prots. Upr. 495, 48–54 (2020)].
V. P. Platonov, M. M. Petrunin, and Yu. N. Shteinikov, “On the finiteness of the number of elliptic fields with given degrees of \(S\)-units and periodic expansion of \(\sqrt {f}\),” Dokl. Math. 100 (2), 1–5 (2019) [transl. from Dokl. Akad. Nauk 488 (3), 9–14 (2019)].
V. P. Platonov, M. M. Petrunin, and Yu. N. Shteinikov, “On the periodicity problem for the continued fraction expansion of elements of hyperelliptic fields with fundamental \(S\)-units of degree at most 11,” Dokl. Math. 104 (5), 258–263 (2021) [transl. from Dokl. Ross. Akad. Nauk, Mat. Inform. Prots. Upr. 500, 45–51 (2021)].
V. P. Platonov, M. M. Petrunin, and V. S. Zhgoon, “On the problem of periodicity of continued fraction expansions of \(\sqrt {f}\) for cubic polynomials over number fields,” Dokl. Math. 102 (1), 288–292 (2020) [transl. from Dokl. Ross. Akad. Nauk, Mat. Inform. Prots. Upr. 493, 32–37 (2020)].
V. P. Platonov, V. S. Zhgoon, and M. M. Petrunin, “On the problem of periodicity of continued fraction expansions of \(\sqrt {f}\) for cubic polynomials \(f\) over algebraic number fields,” Sb. Math. 213 (3), 412–442 (2022) [transl. from Mat. Sb. 213 (3), 139–170 (2022)].
V. P. Platonov, V. S. Zhgoon, M. M. Petrunin, and Yu. N. Shteinikov, “On the finiteness of hyperelliptic fields with special properties and periodic expansion of \(\sqrt {f}\),” Dokl. Math. 98 (3), 641–645 (2018) [transl. from Dokl. Akad. Nauk 483 (6), 609–613 (2018)].
W. M. Schmidt, “On continued fractions and Diophantine approximation in power series fields,” Acta Arith. 95 (2), 139–166 (2000).
A. V. Sutherland, “Constructing elliptic curves over finite fields with prescribed torsion,” Math. Comput. 81 (278), 1131–1147 (2012).
P. Tchebichef, “Sur l’intégration des différentielles qui contiennent une racine carrée d’un polynome du troisième ou du quatrième degré,” J. Math. Pures Appl. 2, 1–42 (1857).
Funding
This work was performed within the state assignment for basic scientific research, project no. FNEF-2022-0011.
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Translated from Trudy Matematicheskogo Instituta imeni V.A. Steklova, 2023, Vol. 320, pp. 278–286 https://doi.org/10.4213/tm4283.
To the blessed memory of Alexey Nikolaevich Parshin
Translated by I. Nikitin
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Platonov, V.P., Petrunin, M.M. New Results on the Periodicity Problem for Continued Fractions of Elements of Hyperelliptic Fields. Proc. Steklov Inst. Math. 320, 258–266 (2023). https://doi.org/10.1134/S008154382301011X
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DOI: https://doi.org/10.1134/S008154382301011X