Growth Rates of Permutation Classes: Categorization Up to the Uncountability Threshold

Document Type

Article

Publication Date

2020

Publisher

Springer

Source Publication

Israel Journal of Mathematics

Source ISSN

0021-2172

Original Item ID

DOI: 10.1007/s11856-020-1964-5

Abstract

In the antecedent paper to this it was established that there is an algebraic number ξ ≈ 2.30522 such that while there are uncountably many growth rates of permutation classes arbitrarily close to ξ, there are only countably many less than ξ. Here we provide a complete characterization of the growth rates less than ξ. In particular, this classification establishes that ξ is the least accumulation point from above of growth rates and that all growth rates less than or equal to ξ are achieved by finitely based classes. A significant part of this classification is achieved via a reconstruction result for sum indecomposable permutations. We conclude by refuting a suggestion of Klazar, showing that ξ is an accumulation point from above of growth rates of finitely based permutation classes.

Comments

Israel Journal of Mathematics, Vol. 236 (2020): 1-43. DOI.

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