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 …

Spectral extrema of Ks, t-minor free graphs–On a conjecture of M. Tait

M Zhai, H Lin - Journal of Combinatorial Theory, Series B, 2022 - Elsevier
Minors play a key role in graph theory, and extremal problems on forbidding minors have
attracted appreciable amount of interest in the past decades. In this paper, we focus on …

A unique characterization of spectral extrema for friendship graphs

M Zhai, R Liu, J Xue - The Electronic Journal of Combinatorics, 2022 - combinatorics.org
Turán-type problem is one of central problems in extremal graph theory. Erdős et al.[J.
Combin. Theory Ser. B 64 (1995) 89-100] obtained the exact Turán number of the friendship …

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 …

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 …

Spectral radius, edge-disjoint cycles and cycles of the same length

H Lin, M Zhai, Y Zhao - arXiv preprint arXiv:2108.09057, 2021 - arxiv.org
In this paper, we give spectral conditions to guarantee the existence of two edge disjoint
cycles and two cycles of the same length. These two results can be seen as spectral …

Spectral extremal graphs for the bowtie

Y Li, L Lu, Y Peng - Discrete Mathematics, 2023 - Elsevier
Let F k be the (friendship) graph obtained from k triangles by sharing a common vertex. The
F k-free graphs of order n which attain the maximal spectral radius was firstly characterized …

Counting substructures and eigenvalues I: triangles

B Ning, M Zhai - European Journal of Combinatorics, 2023 - Elsevier
Motivated by the counting results for color-critical subgraphs by Mubayi (2010), we study the
phenomenon behind Mubayi's theorem from a spectral perspective and start up this problem …

Stability of Woodall's Theorem and Spectral Conditions for Large Cycles

B Li, B Ning - The Electronic Journal of Combinatorics, 2023 - combinatorics.org
In the 1970s, Erdős asked how many edges are needed in a graph on $ n $ vertices, to
ensure the existence of a cycle of length exactly $ nk $. In this paper, we consider the …

Generalizing theorems of Nosal and Nikiforov: Triangles and quadrilaterals

Z Wang - Discrete Mathematics, 2022 - Elsevier
Let ρ (G) be the spectral radius of a graph G with m edges. Nosal's theorem states that if ρ
(G)> m then G contains a triangle. In this article, we give a generalization: any non-bipartite …