A graph-theoretic proof of Cobham's Dichotomy for automatic sequences

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1. Verfasser: Wessel, Mieke
Format: Preprint
Veröffentlicht: 2024
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author Wessel, Mieke
author_facet Wessel, Mieke
contents We give a new graph-theoretic proof of Cobham's Theorem which says that the support of an automatic sequence is either sparse or grows at least like $N^α$ for some $α> 0$. The proof uses the notions of tied vertices and cycle arboressences. With the ideas of the proof we can also give a new interpretation of the rank of a sparse sequence as the height of its cycle arboressence. In the non-sparse case we are able to determine the supremum of possible $α$, which turns out to be the logarithm of an integer root of a Perron number.
format Preprint
id arxiv_https___arxiv_org_abs_2405_11385
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A graph-theoretic proof of Cobham's Dichotomy for automatic sequences
Wessel, Mieke
Combinatorics
Number Theory
We give a new graph-theoretic proof of Cobham's Theorem which says that the support of an automatic sequence is either sparse or grows at least like $N^α$ for some $α> 0$. The proof uses the notions of tied vertices and cycle arboressences. With the ideas of the proof we can also give a new interpretation of the rank of a sparse sequence as the height of its cycle arboressence. In the non-sparse case we are able to determine the supremum of possible $α$, which turns out to be the logarithm of an integer root of a Perron number.
title A graph-theoretic proof of Cobham's Dichotomy for automatic sequences
topic Combinatorics
Number Theory
url https://arxiv.org/abs/2405.11385