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Synchronization and separation in the Johnson schemes

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Alijohani_2017_Schemes_PortugalMath_AAM.pdf (302.8Kb)
Date
09/02/2018
Author
Aljohani, Mohammed
Bamberg, John
Cameron, Peter Jephson
Keywords
Synchronization
Steiner systems
QA Mathematics
T-NDAS
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Abstract
Recently Peter Keevash solved asymptotically the existence question for Steiner systems by showing that S(t,k,n) exists whenever the necessary divisibility conditions on the parameters are satisfied and n is sufficiently large in terms of k and t. The purpose of this paper is to make a conjecture which if true would be a significant extension of Keevash's theorem, and to give some theoretical and computational evidence for the conjecture. We phrase the conjecture in terms of the notions (which we define here) of synchronization and separation for association schemes. These definitions are based on those for permutation groups which grow out of the theory of synchronization in finite automata. In this theory, two classes of permutation groups (called synchronizing and separating) lying between primitive and 2-homogeneous are defined. A big open question is how the permutation group induced by Sn on k-subsets of {1,...,n} fits in this hierarchy; our conjecture would give a solution to this problem for n large in terms of k.
Citation
Aljohani , M , Bamberg , J & Cameron , P J 2018 , ' Synchronization and separation in the Johnson schemes ' , Portugaliae Mathematica , vol. 74 , no. 3 , pp. 213-232 . https://doi.org/10.4171/PM/2003
Publication
Portugaliae Mathematica
Status
Peer reviewed
DOI
https://doi.org/10.4171/PM/2003
ISSN
0032-5155
Type
Journal article
Rights
Copyright © 2017, European Mathematical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.4171/PM/2003
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  • University of St Andrews Research
URL
http://www.ems-ph.org/journals/journal.php?jrn=pm
URI
http://hdl.handle.net/10023/11525

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