Convergence, Finiteness and Periodicity of Several New Algorithms of p-adic Continued Fractions

TL;DR

This paper introduces new algorithms for $p$-adic continued fractions that improve understanding of their properties, including periodicity for quadratic irrationals, and offers bounds on expansion lengths.

Contribution

The paper presents refined $p$-adic continued fraction algorithms with proven periodicity for quadratic irrationals and bounds on partial quotient lengths.

Findings

Algorithms generate periodic expansions for quadratic irrationals.

An upper bound on partial quotient lengths for rational expansions.

One algorithm is the most effective $p$-adic algorithm to date.

Abstract

$p$-adic continued fractions, as an extension of the classical concept of classical continued fractions to the realm of $p$-adic numbers, offering a novel perspective on number representation and approximation. While numerous $p$-adic continued fraction expansion algorithms have been proposed by the researchers, the establishment of several excellent properties, such as the Lagrange Theorem for classic continued fractions, which indicates that every quadratic irrationals can be expanded periodically, remains elusive. In this paper, we present several new algorithms that can be viewed as refinements of the existing $p$-adic continued fraction algorithms. We give an upper bound of the length of partial quotients when expanding rational numbers, and prove that for small primes $p$, our algorithm can generate periodic continued fraction expansions for all quadratic irrationals. As confirmed through experimentation, one of our algorithms can be viewed as the best $p$-adic algorithm available to date. Furthermore, we provide an approach to establish a $p$-adic continued fraction expansion algorithm that could generate periodic expansions for all quadratic irrationals in $\mathbb{Q}_p$ for a given prime $p$.