The influence of cut vertices and eigenvalues on character graphs of solvable groups

TL;DR

This paper explores how the structure and spectral properties of character graphs of solvable groups relate to the groups' algebraic structure, focusing on cut vertices, eigenvalues, and graph regularity.

Contribution

It characterizes the structure of solvable groups with specific character graph properties, including cut vertices, diameter, and eigenvalue constraints.

Findings

Character graphs of solvable groups with a cut vertex and diameter 3 are classified.

Solvable groups with character graphs having at most two eigenvalues are studied.

Bounds are established for the number of edges in character graphs.

Abstract

Given a finite group $G$, the character graph, denoted by $\Delta(G)$, for its irreducible character degrees is a graph with vertex set $\rho(G)$ which is the set of prime numbers that divide the irreducible character degrees of $G$, and with $\{p,q\}$ being an edge if there exist a non-linear $\chi\in {\rm Irr}(G)$ whose degree is divisible by $pq$. In this paper, we discuss the influences of cut vertices and eigenvalues of $\Delta(G)$ on the group structure of $G$. Recently, Lewis and Meng proved the character graph of each solvable group has at most one cut vertex. Now, we determine the structure of character graphs of solvable groups with a cut vertex and diameter $3$. Furthermore, we study solvable groups whose character graphs have at most two distinct eigenvalues. Moreover, we investigate the solvable groups whose character graphs are regular with three distinct eigenvalues. In addition, we give some lower bounds for the number of edges of $\Delta(G)$.