scholarly journals On the relational complexity of a finite permutation group

2015 ◽  
Vol 43 (2) ◽  
pp. 339-374 ◽  
Author(s):  
Gregory Cherlin
Keyword(s):  
Permutation Group ◽  
Finite Permutation Group ◽  
Relational Complexity

scholarly journals ON THE HEIGHT AND RELATIONAL COMPLEXITY OF A FINITE PERMUTATION GROUP

2021 ◽  
pp. 1-40
Author(s):  
NICK GILL ◽  
BIANCA LODÀ ◽  
PABLO SPIGA
Keyword(s):  
Permutation Group ◽  
Model Theory ◽  
Independent Set ◽  
Maximum Size ◽  
Proper Subset ◽  
Permutation Groups ◽  
Finite Permutation Group ◽  
Pointwise Stabilizer ◽  
Relational Complexity

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).

Linear Symmetry Classes

1976 ◽  
Vol 28 (6) ◽  
pp. 1311-1319 ◽  
Author(s):  
L. J. Cummings ◽  
R. W. Robinson
Keyword(s):  
Vector Space ◽  
Permutation Group ◽  
Cyclic Group ◽  
Symmetry Class ◽  
Complex Vector Space ◽  
Complex Vector ◽  
Linear Character ◽  
Finite Permutation Group ◽  
Symmetry Classes ◽  
Finite Dimensional

A formula is derived for the dimension of a symmetry class of tensors (over a finite dimensional complex vector space) associated with an arbitrary finite permutation group G and a linear character of x of G. This generalizes a result of the first author [3] which solved the problem in case G is a cyclic group.

scholarly journals UNDECIDABILITY AND THE DEVELOPABILITY OF PERMUTOIDS AND RIGID PSEUDOGROUPS

2017 ◽  
Vol 5 ◽  
Author(s):  
MARTIN R. BRIDSON ◽  
HENRY WILTON
Keyword(s):  
Recent Work ◽  
Permutation Group ◽  
Inverse Semigroups ◽  
Existence Problem ◽  
Finitely Presented Groups ◽  
Finite Permutation Group ◽  
Finite Set ◽  
Finitely Presented

A permutoid is a set of partial permutations that contains the identity and is such that partial compositions, when defined, have at most one extension in the set. In 2004 Peter Cameron conjectured that there can exist no algorithm that determines whether or not a permutoid based on a finite set can be completed to a finite permutation group. In this note we prove Cameron’s conjecture by relating it to our recent work on the profinite triviality problem for finitely presented groups. We also prove that the existence problem for finite developments of rigid pseudogroups is unsolvable. In an appendix, Steinberg recasts these results in terms of inverse semigroups.

scholarly journals On the involution fixity of simple groups

2021 ◽  
pp. 1-19
Author(s):  
Timothy C. Burness ◽  
Elisa Covato
Keyword(s):  
Fixed Points ◽  
Permutation Group ◽  
Simple Groups ◽  
Classical Groups ◽  
Exceptional Group ◽  
Sporadic Group ◽  
Group Of Lie Type ◽  
Primitive Groups ◽  
Finite Permutation Group

Abstract Let $G$ be a finite permutation group of degree $n$ and let ${\rm ifix}(G)$ be the involution fixity of $G$ , which is the maximum number of fixed points of an involution. In this paper, we study the involution fixity of almost simple primitive groups whose socle $T$ is an alternating or sporadic group; our main result classifies the groups of this form with ${\rm ifix}(T) \leqslant n^{4/9}$ . This builds on earlier work of Burness and Thomas, who studied the case where $T$ is an exceptional group of Lie type, and it strengthens the bound ${\rm ifix}(T) > n^{1/6}$ (with prescribed exceptions), which was proved by Liebeck and Shalev in 2015. A similar result for classical groups will be established in a sequel.

scholarly journals Subgroups of minimal index in polynomial time

2019 ◽  
Vol 19 (01) ◽  
pp. 2050010
Author(s):  
Saveliy V. Skresanov
Keyword(s):  
Permutation Group ◽  
Polynomial Time ◽  
Proper Subgroup ◽  
Polynomial Time Algorithm ◽  
Time Algorithm ◽  
Cayley Table ◽  
Finite Permutation Group ◽  
Minimal Index

By applying an old result of Y. Berkovich, we provide a polynomial-time algorithm for computing the minimal possible index of a proper subgroup of a finite permutation group [Formula: see text]. Moreover, we find that subgroup explicitly and within the same time if [Formula: see text] is given by a Cayley table. As a corollary, we get an algorithm for testing whether or not a finite permutation group acts on a tree non-trivially.

On the Group of a Directed Graph

1966 ◽  
Vol 18 ◽  
pp. 211-220 ◽  
Author(s):  
Robert L. Hemminger
Keyword(s):  
Finite Group ◽  
Permutation Group ◽  
Directed Graph ◽  
Directed Graphs ◽  
Symmetric Case ◽  
Related Question ◽  
Permutation Groups ◽  
Symmetric Graph ◽  
Finite Permutation Group ◽  
Symmetric Graphs

In 1938, Frucht (2) proved that for any given finite group G there exists a finite symmetric graph X such that G(X) is abstractly isomorphic to G. Since G(X) is a permutation group, it is natural to ask the following related question : If P is a given finite permutation group, does there exist a symmetric (and more generally a directed) graph X such that G(X) and P are isomorphic (see Convention below) as permutation groups? The answer for the symmetric case is negative as seen in (3) and more recently in (1). It is the purpose of this paper to deal with this problem further, especially in the directed case. In §3, we supplement Kagno's results (3, pp. 516-520) for symmetric graphs by giving the corresponding results for directed graphs.

Magic letter groups

2007 ◽  
Vol 91 (522) ◽  
pp. 493-499
Author(s):  
Mike Pearson ◽  
Ian Short
Keyword(s):  
Permutation Group ◽  
Isomorphism Type ◽  
Permutation Groups ◽  
Natural Manner ◽  
Finite Permutation Group

Certain numeric puzzles, known as ‘magic letters’, each have a finite permutation group associated with them in a natural manner. We describe how the isomorphism type of these permutation groups relates to the structure of the magic letters.

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