The Newton approximation, the Hurwitz continued fraction, and the Sierpinski series for relatively quadratic units over certain imaginary quadratic number fields

Fuente: arXiv
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Main Authors: Saito, Asaki, Tamura, Jun-Ichi
Format: Preprint
Published: 2025
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author Saito, Asaki
Tamura, Jun-Ichi
author_facet Saito, Asaki
Tamura, Jun-Ichi
contents The objective of this paper is to show (a)=(b)=(c) as rational functions of $T$, $U$ for (a), (b), (c) given by (a) continued fractions of length $2^{n+1}-1$ with explicit partial denominators in $\left\{-T,U^{-1}T\right\}$, (b) truncated series $\sum_{0\le m\le n} \left(U^{2^m}/\left(h_0(T)h_1(T,U) \cdots h_m(T,U)\right)\right)$ with $h_n$ defined by $h_0:=T$ and $h_{n+1}(T,U):=h_n(T,U)^2-2U^{2^n} (n \geq 0)$, (c) $(n+1)$-fold iteration $F^{(n+1)}(0)= F^{(n+1)}(0,T,U)$ of $F(X)= F(X,T,U) :=X-f(X)/\frac{df}{dX}(X)$ for $f(X)=X^2-T X+U$, and to find explicit equalities among truncated Hurwitz continued fraction expansion of relatively quadratic units $α\in \mathbb{C}$ over imaginary quadratic fields $\mathbb{Q}\left(\sqrt{-1}\right)$, $\mathbb{Q}\left(\sqrt{-3}\right)$, rapidly convergent complex series called the Sierpinski series, and the Newton approximation of $α$ on the complex plane. We also give an estimate of the error of the Newton approximation of the unit $α$.
format Preprint
id arxiv_https___arxiv_org_abs_2510_15498
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Newton approximation, the Hurwitz continued fraction, and the Sierpinski series for relatively quadratic units over certain imaginary quadratic number fields
Saito, Asaki
Tamura, Jun-Ichi
Number Theory
Primary 11A55, 30B70, Secondary 49M15
The objective of this paper is to show (a)=(b)=(c) as rational functions of $T$, $U$ for (a), (b), (c) given by (a) continued fractions of length $2^{n+1}-1$ with explicit partial denominators in $\left\{-T,U^{-1}T\right\}$, (b) truncated series $\sum_{0\le m\le n} \left(U^{2^m}/\left(h_0(T)h_1(T,U) \cdots h_m(T,U)\right)\right)$ with $h_n$ defined by $h_0:=T$ and $h_{n+1}(T,U):=h_n(T,U)^2-2U^{2^n} (n \geq 0)$, (c) $(n+1)$-fold iteration $F^{(n+1)}(0)= F^{(n+1)}(0,T,U)$ of $F(X)= F(X,T,U) :=X-f(X)/\frac{df}{dX}(X)$ for $f(X)=X^2-T X+U$, and to find explicit equalities among truncated Hurwitz continued fraction expansion of relatively quadratic units $α\in \mathbb{C}$ over imaginary quadratic fields $\mathbb{Q}\left(\sqrt{-1}\right)$, $\mathbb{Q}\left(\sqrt{-3}\right)$, rapidly convergent complex series called the Sierpinski series, and the Newton approximation of $α$ on the complex plane. We also give an estimate of the error of the Newton approximation of the unit $α$.
title The Newton approximation, the Hurwitz continued fraction, and the Sierpinski series for relatively quadratic units over certain imaginary quadratic number fields
topic Number Theory
Primary 11A55, 30B70, Secondary 49M15
url https://arxiv.org/abs/2510.15498