Title
Rainbow triangles and the Caccetta‐Häggkvist conjecture
Abstract
A famous conjecture of Caccetta and Haggkvist is that in a digraph on n vertices and minimum outdegree at least n/r there is a directed cycle of length r or less. We consider the following generalization: in an undirected graph on n vertices, any collection of n disjoint sets of edges, each of size at least n/r, has a rainbow cycle of length r or less. We focus on the case r = 3 and prove the existence of a rainbow triangle under somewhat stronger conditions than in the conjecture. In our main result, whenever n is larger than a suitable polynomial in k, we determine the maximum number of edges in an n-vertex edge-colored graph where all color classes have size at most k and there is no rainbow triangle. Moreover, we characterize the extremal graphs for this problem.
Year
DOI
Venue
2019
10.1002/jgt.22457
JOURNAL OF GRAPH THEORY
Keywords
DocType
Volume
Caccetta-Haggkvist,edge-colored graph,rainbow triangles
Journal
92.0
Issue
ISSN
Citations 
4.0
0364-9024
0
PageRank 
References 
Authors
0.34
0
3
Name
Order
Citations
PageRank
Ron Aharoni I1138.92
Matthew DeVos200.34
Ron Holzman328743.78