Maximizing the number of $x$-colorings of $4$-chromatic graphs

TL;DR

This paper investigates the maximum number of colorings in connected 4-chromatic graphs, proposing a reduction to a finite family of graphs to verify a conjecture about extremal graph colorings.

Contribution

It reduces the problem of maximizing colorings to checking a finite set of graphs, advancing understanding of extremal properties in graph coloring.

Findings

Existence of a finite family of graphs for verification

Reduction of the problem to finite cases

Support for the conjecture under certain conditions

Abstract

Let $\mathcal{C}_4(n)$ be the family of all connected $4$-chromatic graphs of order $n$. Given an integer $x\geq 4$, we consider the problem of finding the maximum number of $x$-colorings of a graph in $\mathcal{C}_4(n)$. It was conjectured that the maximum number of $x$-colorings is equal to $(x)_{\downarrow 4}(x-1)^{n-4}$ and the extremal graphs are those which have clique number $4$ and size $n+2$. In this article, we reduce this problem to a \textit{finite} family of graphs. We show that there exist a finite family $\mathcal{F}$ of connected $4$-chromatic graphs such that if the number of $x$-colorings of every graph $G$ in $\mathcal{F}$ is less than $(x)_{\downarrow 4}(x-1)^{|V(G)|-4}$ then the conjecture holds to be true.