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Transversal Ck-factors in subgraphs of the balanced blow-up of Ck

Published online by Cambridge University Press:  30 May 2022

Beka Ergemlidze
Affiliation:
Department of Mathematics and Statistics, University of South Florida, Tampa, FL33620, USA.
Theodore Molla*
Affiliation:
Department of Mathematics and Statistics, University of South Florida, Tampa, FL33620, USA.
*
*Corresponding author. Email: molla@usf.edu

Abstract

For a subgraph $G$ of the blow-up of a graph $F$ , we let $\delta ^*(G)$ be the smallest minimum degree over all of the bipartite subgraphs of $G$ induced by pairs of parts that correspond to edges of $F$ . Johansson proved that if $G$ is a spanning subgraph of the blow-up of $C_3$ with parts of size $n$ and $\delta ^*(G) \ge \frac{2}{3}n + \sqrt{n}$ , then $G$ contains $n$ vertex disjoint triangles, and presented the following conjecture of Häggkvist. If $G$ is a spanning subgraph of the blow-up of $C_k$ with parts of size $n$ and $\delta ^*(G) \ge \left(1 + \frac 1k\right)\frac n2 + 1$ , then $G$ contains $n$ vertex disjoint copies of $C_k$ such that each $C_k$ intersects each of the $k$ parts exactly once. A similar conjecture was also made by Fischer and the case $k=3$ was proved for large $n$ by Magyar and Martin.

In this paper, we prove the conjecture of Häggkvist asymptotically. We also pose a conjecture which generalises this result by allowing the minimum degree conditions in each bipartite subgraph induced by pairs of parts of $G$ to vary. We support this new conjecture by proving the triangle case. This result generalises Johannson’s result asymptotically.

MSC classification

Type
Paper
Copyright
© The Author(s), 2022. Published by Cambridge University Press

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Footnotes

Research supported in part by NSF Grant DMS 1800761.

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