On the approximation gain for abc-triples
Benne de Weger
TL;DR
This paper extends the abc-triple framework by introducing real, $p$-adic, and combined approximation gains to quantify how well an abc-triple can be approximated through structured factorizations. It defines real enhancements $\mathrm{rrad}_d$, $\mathrm{rag}_d$, and $\mathrm{rpg}_d$, and their extremal versions $\mathrm{rag}$ and $\mathrm{rpg}$, linking them to the $abc$-quality $qu$. It then develops $p$-adic analogues via $\mathrm{mrad}$, $\mathrm{mag}$, $\mathrm{mpg}$ and their single- and multi-prime variants, with a theorem that the multi-$p$-adic gain dominates the real gain, so the combined gain reduces to the multi-$p$-adic gain. The authors illustrate the framework with concrete examples (notably Reyssat’s triple) and provide extensive computational results on massive abc-triple datasets, demonstrating both high gains and the distribution of gains. The work provides a comprehensive toolkit for assessing and comparing abc-triples beyond the classical surrogate surd-based constructions, with online data resources for broader use and SEO-friendly discoverability.
Abstract
The concept of approximation gain was introduced recently by Müller and Taktikos for some abc-triples related to convergents of surds, where there is a relatively large gap between min{a,b,c} and max{a,b,c}. This note proposes a generalization of the concept to all abc-triples, with several variants. Extensive numerical computations are provided.
