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Good sequencings of partial Steiner systems

Horsley, Daniel orcid logoORCID: 0000-0001-9971-7148 and Ó Catháin, Padraig orcid logoORCID: 0000-0002-7963-9688 (2022) Good sequencings of partial Steiner systems. 0925-1022, 90 . pp. 2375-2383. ISSN Designs, Codes and Cryptography

Abstract
A partial (n, k, t)λ-system is a pair(X, B) where X is an n-set of vertices and B is a collection of k-subsets of X called blocks such that each t-set of vertices is a subset of at most λ blocks. A sequencing of such a system is a labelling of its vertices with distinct elements of {0,..., n − 1}. A sequencing is -block avoiding or, more briefly, -good if no block is contained in a set of vertices with consecutive labels. Here we give a short proof that, for fixed k, t and λ, any partial (n, k, t)λ-system has an -good sequencing for some = �(n1/t ) as n becomes large. This improves on results of Blackburn and Etzion, and of Stinson and Veitch. Our result is perhaps of most interest in the case k = t +1 where results of Kostochka, Mubayi and Verstraëte show that the value of cannot be increased beyond �((n log n)1/t ). A special case of our result shows that every partial Steiner triple system (partial (n, 3, 2)1- system) has an -good sequencing for each positive integer 0.0908 n1/2.
Metadata
Item Type:Article (Published)
Refereed:Yes
Uncontrolled Keywords:Point sequencing; Point ordering; Steiner system
Subjects:Mathematics
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Humanities and Social Science > Fiontar agus Scoil na Gaeilge
Publisher:Springer
Official URL:https://doi.org/10.1007/s10623-022-01085-5
Copyright Information:© 2022 The Authors.
Funders:Open Access funding enabled and organized by CAUL and its Member Institutions, Australian Research Council grants DP150100506 and FT160100048.
ID Code:29110
Deposited On:05 Oct 2023 12:26 by Vidatum Academic . Last Modified 05 Oct 2023 12:26
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