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# Tree automata and pigeonhole classes of matroids -- I

journal contribution

posted on 2021-12-01, 19:46 authored by Daryl Funk, Dillon Mayhew, Mike NewmanHlineny's Theorem shows that any sentence in the monadic second-order logic
of matroids can be tested in polynomial time, when the input is limited to a
class of F-representable matroids with bounded branch-width (where F is a
finite field). If each matroid in a class can be decomposed by a subcubic tree
in such a way that only a bounded amount of information flows across displayed
separations, then the class has bounded decomposition-width. We introduce the
pigeonhole property for classes of matroids: if every subclass with bounded
branch-width also has bounded decomposition-width, then the class is
pigeonhole. An efficiently pigeonhole class has a stronger property, involving
an efficiently-computable equivalence relation on subsets of the ground set. We
show that Hlineny's Theorem extends to any efficiently pigeonhole class. In a
sequel paper, we use these ideas to extend Hlineny's Theorem to the classes of
fundamental transversal matroids, lattice path matroids, bicircular matroids,
and H-gain-graphic matroids, where H is any finite group. We also give a
characterisation of the families of hypergraphs that can be described via tree
automata: a family is defined by a tree automaton if and only if it has bounded
decomposition-width. Furthermore, we show that if a class of matroids has the
pigeonhole property, and can be defined in monadic second-order logic, then any
subclass with bounded branch-width has a decidable monadic second-order theory.

## History

## Preferred citation

Funk, D., Mayhew, D. & Newman, M. (2019). Tree automata and pigeonhole classes of matroids -- I. http://arxiv.org/abs/1910.04360v3## Publication date

2019-10-10## Usage metrics

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