Complete bipartite graphs without small rainbow stars

TL;DR

This paper investigates the structure of bipartite graphs avoiding small rainbow stars and determines exact Gallai-Ramsey numbers for certain bipartite graphs with respect to unions of cycles, paths, and stars.

Contribution

It provides a structural theorem for bipartite graphs without rainbow $K_{1,3}$ and calculates exact bipartite Gallai-Ramsey numbers for specific graph configurations.

Findings

Structural characterization of bipartite graphs without rainbow $K_{1,3}$

Exact Gallai-Ramsey numbers for $P_4$, $P_5$, and $K_{1,3}$ with unions of cycles, paths, and stars

Extensions of bipartite Gallai-Ramsey theory to new graph classes

Abstract

The $k$-edge-colored bipartite Gallai-Ramsey number $\operatorname{bgr}_k(G:H)$ is defined as the minimum integer $n$ such that $n^2\geq k$ and for every $N\geq n$, every edge-coloring (using all $k$ colors) of complete bipartite graph $K_{N,N}$ contains a rainbow copy of $G$ or a monochromatic copy of $H$. In this paper, we first study the structural theorem on the complete bipartite graph $K_{n,n}$ with no rainbow copy of $K_{1,3}$. Next, we utilize the results to prove the exact values of $\operatorname{bgr}_{k}(P_4: H)$, $\operatorname{bgr}_{k}(P_5: H)$, $\operatorname{bgr}_{k}(K_{1,3}: H)$, where $H$ is a various union of cycles and paths and stars.