A survey on spectral conditions for some extremal graph problems

Y Li, W Liu, L Feng - arXiv preprint arXiv:2111.03309, 2021 - arxiv.org
This survey is two-fold. We first report new progress on the spectral extremal results on the
Tur\'{a} n type problems in graph theory. More precisely, we shall summarize the spectral …

Adjacency eigenvalues of graphs without short odd cycles

S Li, W Sun, Y Yu - Discrete Mathematics, 2022 - Elsevier
It is well known that spectral Turán type problem is one of the most classical problems in
graph theory. In this paper, we consider the spectral Turán type problem. Let G be a graph …

A sharp upper bound on the spectral radius of C5-free/C6-free graphs with given size

G Min, Z Lou, Q Huang - Linear Algebra and its Applications, 2022 - Elsevier
Let S n, 2 be the graph obtained by joining each vertex of K 2 to n− 2 isolated vertices, and
let S n, 2− be the graph obtained from S n, 2 by deleting an edge incident to a vertex of …

Spectral extremal graphs for fan graphs

L Yu, Y Li, Y Peng - Discrete Mathematics, 2025 - Elsevier
A well-known result of Nosal states that a graph G with m edges and λ (G)> m contains a
triangle. Nikiforov [Combin. Probab. Comput. 11 (2002)] extended this result to cliques by …

The maximum spectral radius of non-bipartite graphs forbidding short odd cycles

Y Li, Y Peng - arXiv preprint arXiv:2204.09884, 2022 - arxiv.org
It is well-known that eigenvalues of graphs can be used to describe structural properties and
parameters of graphs. A theorem of Nosal states that if $ G $ is a triangle-free graph with $ m …

Refinement on spectral Turán's theorem

Y Li, Y Peng - SIAM Journal on Discrete Mathematics, 2023 - SIAM
A well-known result in extremal spectral graph theory, known as Nosal's theorem, states that
if is a triangle-free graph on vertices, then, equality holds if and only if. Nikiforov [Linear …

On the spectral radius of graphs without a gem

Y Zhang, L Wang - Discrete Mathematics, 2024 - Elsevier
The gem is the 5-vertex graph consisting of a 4-vertex path plus a vertex adjacent to each
vertex of the path. A graph is said to be gem-free if it does not contain gem as a subgraph. In …

Spectral extrema of graphs with fixed size: forbidden fan graph, friendship graph or theta graph

S Li, S Zhao, L Zou - arXiv preprint arXiv:2409.15918, 2024 - arxiv.org
It is well-known that Brualdi-Hoffman-Tur\'an-type problem asks what is the maximum
spectral radius $\lambda (G) $ of an $ F $-free graph $ G $ with $ m $ edges? It can be …

On the Aα-spectral radius of graphs with given size and diameter

Z Feng, W Wei - Linear Algebra and its Applications, 2022 - Elsevier
Abstract In 2017, Nikiforov [12] proposed the A α-matrix of a graph G, which is defined as the
convex linear combination of the adjacency matrix A (G) and the diagonal matrix of degrees …

Unsolved problems in spectral graph theory

L Liu, B Ning - arXiv preprint arXiv:2305.10290, 2023 - arxiv.org
Spectral graph theory is a captivating area of graph theory that employs the eigenvalues and
eigenvectors of matrices associated with graphs to study them. In this paper, we present a …