A tournament approach to pattern avoiding matrices

Asaf Shapira, Raphael Yuster

Research output: Contribution to journalArticlepeer-review

Abstract

We consider the following Turán-type problem: given a fixed tournament H, what is the least integer t = t(n,H) so that adding t edges to any n-vertex tournament, results in a digraph containing a copy of H. Similarly, what is the least integer t = t(Tn,H) so that adding t edges to the n-vertex transitive tournament, results in a digraph containing a copy of H. Besides proving several results on these problems, our main contributions are the following:Pach and Tardos conjectured that if M is an acyclic 0/1 matrix, then any n × n matrix with n(log n)O(1) entries equal to 1 contains the pattern M. We show that this conjecture is equivalent to the assertion that t(Tn,H) = n(log n)O(1) if and only if H belongs to a certain (natural) family of tournaments.We propose an approach for determining if t(n,H) = n(log n)O(1). This approach combines expansion in sparse graphs, together with certain structural characterizations of H-free tournaments. Our result opens the door for using structural graph theoretic tools in order to settle the Pach–Tardos conjecture.

Original languageEnglish
Pages (from-to)477-505
Number of pages29
JournalIsrael Journal of Mathematics
Volume217
Issue number1
DOIs
StatePublished - 1 Mar 2017

Bibliographical note

Publisher Copyright:
© 2017, Hebrew University of Jerusalem.

ASJC Scopus subject areas

  • Mathematics (all)

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