Tree Bricks and Finite Tree Automata
Abstract
Let Λ=KQ/I be a finite-dimensional zero-relation algebra. We encode Crawley--Boevey tree modules over Λ by finite rooted trees labelled by arrows of Q and their formal inverses, and construct a deterministic finite bottom-up tree automaton recognizing exactly these encodings. We define an accepted tree to be an automata-induced tree brick when it has no non-trivial factor--image self-overlap, and use Crawley--Boevey's graph-map basis to prove that this is equivalent to brickness of the associated tree module. We also introduce local colourings of Q1 and show that the arrow alphabet can be compressed without changing the tree data, graph maps, or brick property. The optimal number of colours for such a compression is the maximum of the in-degree and out-degree of Q. We conclude by asking whether the tree language consisting only of bricks is regular.
Related
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BibTeX
@misc{sengupta2026tree,
title = {{Tree Bricks and Finite Tree Automata}},
author = {Annoy Sengupta},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22406},
eprint = {2609.22406},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22406},
}
RIS
TY - UNPB
TI - Tree Bricks and Finite Tree Automata
AU - Annoy Sengupta
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22406
UR - https://arxiv.org/abs/2609.22406
AB - Let Λ=KQ/I be a finite-dimensional zero-relation algebra. We encode Crawley--Boevey tree modules over Λ by finite rooted trees labelled by arrows of Q and their formal inverses, and construct a deterministic finite bottom-up tree automaton recognizing exactly these encodings. We define an accepted tree to be an automata-induced tree brick when it has no non-trivial factor--image self-overlap, and use Crawley--Boevey's graph-map basis to prove that this is equivalent to brickness of the associated tree module. We also introduce local colourings of Q_1 and show that the arrow alphabet can be compressed without changing the tree data, graph maps, or brick property. The optimal number of colours for such a compression is the maximum of the in-degree and out-degree of Q. We conclude by asking whether the tree language consisting only of bricks is regular.
ER -