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On deficiency problems for graphs

Published online by Cambridge University Press:  27 September 2021

Andrea Freschi
Affiliation:
School of Mathematics, University of Birmingham, Birmingham, B15 2TT, UK
Joseph Hyde
Affiliation:
Mathematics Institute, Zeeman Building, University of Warwick, Coventry CV4 7AL, UK
Andrew Treglown*
Affiliation:
School of Mathematics, University of Birmingham, Birmingham, B15 2TT, UK
*
*Corresponding author. Email: a.c.treglown@bham.ac.uk

Abstract

Motivated by analogous questions in the setting of Steiner triple systems and Latin squares, Nenadov, Sudakov and Wagner [Completion and deficiency problems, Journal of Combinatorial Theory Series B, 2020] recently introduced the notion of graph deficiency. Given a global spanning property $\mathcal P$ and a graph $G$ , the deficiency $\text{def}(G)$ of the graph $G$ with respect to the property $\mathcal P$ is the smallest non-negative integer t such that the join $G*K_t$ has property $\mathcal P$ . In particular, Nenadov, Sudakov and Wagner raised the question of determining how many edges an n-vertex graph $G$ needs to ensure $G*K_t$ contains a $K_r$ -factor (for any fixed $r\geq 3$ ). In this paper, we resolve their problem fully. We also give an analogous result that forces $G*K_t$ to contain any fixed bipartite $(n+t)$ -vertex graph of bounded degree and small bandwidth.

Type
Paper
Copyright
© The Author(s), 2021. Published by Cambridge University Press

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