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Tur\'{a}n type extremal problem is how to maximize the number of edges over all graphs which do not contain fixed forbidden subgraphs. Similarly, spectral Tur\'{a}n type extremal problem is how to maximize (signless Laplacian) spectral…

Combinatorics · Mathematics 2020-07-20 Ming-Zhu Chen , A-Ming Liu , Xiao-Dong Zhang

In this paper, we establish a tight sufficient condition for the Hamiltonicity of graphs with large minimum degree in terms of the signless Laplacian spectral radius and characterize all extremal graphs. Moreover, we prove a similar result…

Combinatorics · Mathematics 2017-10-25 Yawen Li , Yao liu , Xing Peng

In this paper we establish some spectral conditions for a graph to be Hamilton-connected in terms of the spectral radius of the adjacency matrix or the signless Laplacian of the graph or its complement. For the existence of Hamiltonian…

Combinatorics · Mathematics 2014-09-19 Gui-Dong Yu , Yi-Zheng Fan

In this paper, we study the Hamiltonicity of graphs with large minimum degree. Firstly, we present some conditions for a simple graph to be Hamilton-connected and traceable from every vertex in terms of the spectral radius of the graph or…

Combinatorics · Mathematics 2017-11-29 Guidong Yu , Yi Fang , Yizheng Fan , Gaixiang Cai

In this paper, we present some spectral sufficient conditions for a graph to be Hamilton-connected in terms of the spectral radius or signless Laplacian spectral radius of the graph. Our results improve some previous work.

Combinatorics · Mathematics 2017-11-09 Qiannan Zhou , Ligong Wang , Yong Lu

In this paper, we give sufficient conditions on the spectral radius for a bipartite graph to Hamiltonian and traceable, which expand the results of Lu, Liu and Tian (2012) [10]. Furthermore, we also present tight sufficient conditions on…

Combinatorics · Mathematics 2015-07-07 Ruifang Liu , Wai Chee Shiu , Jie Xue

A graph $G$ is $k$-edge-Hamiltonian if any collection of vertex-disjoint paths with at most $k$ edges altogether belong to a Hamiltonian cycle in $G$. A graph $G$ is $k$-Hamiltonian if for all $S\subseteq V(G)$ with $|S|\le k$, the subgraph…

Combinatorics · Mathematics 2024-04-09 Yongtao Li , Yuejian Peng

The Tur\'an type extremal problem asks to maximize the number of edges over all graphs which do not contain fixed subgraphs. Similarly, the spectral Tur\'an type extremal problem asks to maximize spectral radius of all graphs which do not…

Combinatorics · Mathematics 2018-01-23 Ming-Zhu Chen , A-Ming Liu , Xiao-Dong Zhang

We study a spectral analog of the Tur\'an problem for simplicial complexes. Specifically, we consider the extremal problem of maximizing the signless Laplacian spectral radius among simplicial complexes without holes. We determine the…

Combinatorics · Mathematics 2026-05-04 Yi-Zheng Fan , Chuan-Ming She , Huan-Zhi Zhang

Let ${\rm EX}(n,H)$ and ${\rm SPEX}(n,H)$ denote the families of $n$-vertex $H$-free graphs with the maximum size and the maximum spectral radius, respectively. A graph $H$ is said to be spectral-consistent if ${\rm SPEX}(n,H)\subseteq {\rm…

Combinatorics · Mathematics 2026-03-24 Longfei Fang , Sergey Goryainov , Denis Krotov , Huiqiu Lin , Mingqing Zhai

In this paper, first, we establish a sufficient condition for a bipartite graph to be Hamilton-connected. Furthermore, we also give two sufficient conditions on distance signless Laplacian spectral radius for a graph to be…

Combinatorics · Mathematics 2016-10-25 Qiannan Zhou , Ligong Wang

The classical spectral Tur\'{a}n problem is to determine the maximum spectral radius of an $\mathcal{F}$-free graph of order $n$. Zhai and Wang [Linear Algebra Appl, 437 (2012) 1641-1647] determined the maximum spectral radius of…

Combinatorics · Mathematics 2025-08-08 Mingsong Qin , Dan Li

An important theorem about the spectral Tur\'an problem of $K_{a,b}$ was largely developed in separate papers. Recently it was completely resolved by Zhai and Lin [J. Comb. Theory, Ser. B 157 (2022) 184-215], which also confirms a…

Combinatorics · Mathematics 2024-12-10 Xingyu Lei , Shuchao Li

It is well known that spectral Tur\'{a}n type problem is one of the most classical {problems} in graph theory. In this paper, we consider the spectral Tur\'{a}n type problem. Let $G$ be a graph and let $\mathcal{G}$ be a set of graphs, we…

Combinatorics · Mathematics 2021-09-13 Shuchao Li , Wanting Sun , Yuantian Yu

Keevash, Lenz and Mubayi developed a general criterion for hypergraph spectral extremal problems in their seminal work (SIAM J. Discrete Math., 2014). Their framework shows that extremal results on the $\alpha$-spectral radius (for $\alpha…

Combinatorics · Mathematics 2025-09-05 Jian Zheng , Honghai Li , Yi-Zheng Fan

Let $\mathcal{H}=(V, E)$ be an $r$-uniform hypergraph on $n$ vertices. The signless Laplacian spectral radius of $\mathcal{H}$ is defined as the maximum modulus of the eigenvalues of the tensor…

Combinatorics · Mathematics 2026-01-16 Yongchun Lu , Jiadong Wu , Liying Kang

In this paper, we present a spectral sufficient condition for a graph to be Hamilton-connected in terms of signless Laplacian spectral radius with large minimum degree.

Combinatorics · Mathematics 2017-12-01 Qiannan Zhou , Ligong Wang , Yong Lu

We investigate quantum graphs with infinitely many vertices and edges without the common restriction on the geometry of the underlying metric graph that there is a positive lower bound on the lengths of its edges. Our central result is a…

Mathematical Physics · Physics 2018-10-30 Pavel Exner , Aleksey Kostenko , Mark Malamud , Hagen Neidhardt

Let $F$ be a graph and $\SPEX (n, F)$ be the class of $n$-vertex graphs which attain the maximum spectral radius and contain no $F$ as a subgraph. Let $\EX (n, F)$ be the family of $n$-vertex graphs which contain maximum number of edges and…

Combinatorics · Mathematics 2026-04-03 Lele Liu , Bo Ning

In this paper we consider spectral extremal problems for hypergraphs. We give two general criteria under which such results may be deduced from `strong stability' forms of the corresponding (pure) extremal results. These results hold for…

Combinatorics · Mathematics 2014-03-07 Peter Keevash , John Lenz , Dhruv Mubayi
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