Additive systems for $\mathbb{Z}$ are undecidable
Combinatorics
2026-04-14 v2 Logic in Computer Science
Abstract
What are the collections of sets such that any has exactly one representation as with ? The answer for instead of is given by a theorem of de Bruijn. We describe a family of natural candidate collections for , which we call canonical collections. Translating the problem into the language of dynamical systems, we show that the question of whether the sumset of a canonical collection covers the entire is difficult: specifically, there is a collection for which this question is equivalent to the Collatz conjecture, and there is a well-behaved family of collections for which this question is equivalent to the universal halting problem for Fractran and is therefore undecidable.
Keywords
Cite
@article{arxiv.2508.17285,
title = {Additive systems for $\mathbb{Z}$ are undecidable},
author = {Andrei Zabolotskii},
journal= {arXiv preprint arXiv:2508.17285},
year = {2026}
}
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11 pages