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ON THE HEIGHT AND RELATIONAL COMPLEXITY OF A FINITE PERMUTATION GROUP

Part of: Permutation groups

Published online by Cambridge University Press:  13 July 2021

NICK GILL Open the ORCID record for NICK GILL [Opens in a new window] ,
BIANCA LODÀ Open the ORCID record for BIANCA LODÀ [Opens in a new window]  and
PABLO SPIGA Open the ORCID record for PABLO SPIGA [Opens in a new window]
NICK GILL
Affiliation:
Department of Mathematics, University of South Wales, Treforest CF37 1DL, United Kingdomnick.gill@southwales.ac.uk
BIANCA LODÀ
Affiliation:
Department of Mathematics, University of South Wales, TreforestCF37 1DL, United Kingdombianca.loda@southwales.ac.uk
PABLO SPIGA
Affiliation:
Dipartimento di Matematica e Applicazioni, University of Milano-Bicocca, Via Cozzi 55, 20125Milano, Italypablo.spiga@unimib.it
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Abstract

Let G be a permutation group on a set $\Omega $ of size t. We say that $\Lambda \subseteq \Omega $ is an independent set if its pointwise stabilizer is not equal to the pointwise stabilizer of any proper subset of $\Lambda $ . We define the height of G to be the maximum size of an independent set, and we denote this quantity $\textrm{H}(G)$ . In this paper, we study $\textrm{H}(G)$ for the case when G is primitive. Our main result asserts that either $\textrm{H}(G)< 9\log t$ or else G is in a particular well-studied family (the primitive large–base groups). An immediate corollary of this result is a characterization of primitive permutation groups with large relational complexity, the latter quantity being a statistic introduced by Cherlin in his study of the model theory of permutation groups. We also study $\textrm{I}(G)$ , the maximum length of an irredundant base of G, in which case we prove that if G is primitive, then either $\textrm{I}(G)<7\log t$ or else, again, G is in a particular family (which includes the primitive large–base groups as well as some others).

Keywords

permutation groupheight of a permutation grouprelational complexitybase size

MSC classification

Primary: 20B25: Finite automorphism groups of algebraic, geometric, or combinatorial structures
Secondary: 20B15: Primitive groups
Type
Article
Information
Nagoya Mathematical Journal , Volume 246 , June 2022 , pp. 372 - 411
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Copyright
© (2021) The Authors. The publishing rights in this article are licenced to Foundation Nagoya Mathematical Journal under an exclusive license

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Footnotes

*

Nick Gill and Pablo Spiga would like to acknowledge the support of the Engineering and Physical Sciences Research Council grant EP/R028702/1 over the course of this research.

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