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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

If $\Gamma$ is a graph for which every edge is in exactly one clique of order $\omega$, then one can form a new graph with vertex set equal to these cliques. This is a generalization of the line graph of $\Gamma$. We discover many general…

Combinatorics · Mathematics 2026-05-25 Connor Phillips

A graph is called $k$-extendable if each $k$-matching can be extended to a perfect matching. We give spectral conditions for the $k$-extendability of graphs and bipartite graphs using Tutte-type and Hall-type structural characterizations.…

Combinatorics · Mathematics 2023-03-31 Yuke Zhang , Edwin R. van Dam

We introduce a zeta function of digraphs that determines, and is determined by, the spectra of all linear combinations of the adjacency matrix, its transpose, the out-degree matrix, and the in-degree matrix. In particular, zeta-equivalence…

Spectral Theory · Mathematics 2015-05-15 Peter Herbrich

The study of spectral graph determination is a fascinating area of research in spectral graph theory and algebraic combinatorics. This field focuses on examining the spectral characterization of various classes of graphs, developing methods…

Combinatorics · Mathematics 2025-04-14 Igal Sason , Noam Krupnik , Suleiman Hamud , Abraham Berman

A signed bipartite graph G(U, V) is a bipartite graph in which each edge is assigned a positive or a negative sign. The signed degree of a vertex x in G(U, V) is the number of positive edges incident with x less the number of negative edges…

Combinatorics · Mathematics 2007-05-23 S. Pirzada , T. A. Naikoo , F. A. Dar

Signed graphs encode positive (attractive) and negative (repulsive) relations between nodes. We extend spectral clustering to signed graphs via the one-parameter family of Signed Power Mean Laplacians, defined as the matrix power mean of…

Machine Learning · Computer Science 2019-05-16 Pedro Mercado , Francesco Tudisco , Matthias Hein

Spectral features are widely incorporated within Graph Neural Networks (GNNs) to improve their expressive power, or their ability to distinguish among non-isomorphic graphs. One popular example is the usage of graph Laplacian eigenvectors…

Machine Learning · Computer Science 2025-09-29 Snir Hordan , Maya Bechler-Speicher , Gur Lifshitz , Nadav Dym

A $k$-uniform hypergraph $G=(V,E)$ is called odd-bipartite ([5]), if $k$ is even and there exists some proper subset $V_1$ of $V$ such that each edge of $G$ contains odd number of vertices in $V_1$. Odd-bipartite hypergraphs are…

Combinatorics · Mathematics 2014-03-20 Jia-Yu Shao , Hai-Ying Shan , Bao-feng Wu

A signed graph is a graph in which every edge carries a $+$ or a $-$ sign. In this paper, we determine the signed graphs with maximum spectral radius among all unbalanced signed graphs with fixed order that contain neither negative…

Combinatorics · Mathematics 2024-07-24 Yiting Cai , Bo Zhou

We consider unitary graphs attached to Z_d^n using an analogue of the Euclidean distance. These graphs are shown to be integral when n is odd or the dimension d is even.

Combinatorics · Mathematics 2008-07-17 Si Li , Le Anh Vinh

We consider the problem of finding universal bounds of "isoperimetric" or "isodiametric" type on the spectral gap of the Laplacian on a metric graph with natural boundary conditions at the vertices, in terms of various analytical and…

Spectral Theory · Mathematics 2016-08-24 James B. Kennedy , Pavel Kurasov , Gabriela Malenova , Delio Mugnolo

Graph Laplacians on finite compact metric graphs are considered under the assumption that the matching conditions at the graph vertices are of either $\delta$ or $\delta'$ type. In either case, an infinite series of trace formulae which…

Mathematical Physics · Physics 2014-04-01 Yulia Ershova , Alexander V. Kiselev

A graph is said to be determined by its signless Laplacian spectrum (abbreviated as DQS) if no other non-isomorphic graph shares the same signless Laplacian spectrum. In this paper, we establish the following results: (1). Every graph of…

Combinatorics · Mathematics 2025-08-24 Jiachang Ye , Zoran Stanić , Jianguo Qian

We consider signed graphs, i.e, graphs with positive or negative signs on their edges. We construct some families of bipartite signed graphs with only two distinct eigenvalues. This leads to constructing infinite families of regular…

Combinatorics · Mathematics 2019-07-23 F. Ramezani

In this paper, we investigate the Moore-Penrose inversion of a simple connected graph. We analyze qualitative, statistical, and extreme properties of spectral indices of signable pseudo-invertible graphs. We introduce and analyze a wide…

Combinatorics · Mathematics 2024-03-11 Sona Pavlikova , Daniel Sevcovic

In this paper, we examine covering graphs that are obtained from the $d$-dimensional integer lattice by adding pendant edges. In the case of $d=1$, we show that the Laplacian on the graph has a spectral gap and establish a necessary and…

Mathematical Physics · Physics 2013-04-17 Aktito Suzuki

Let G be a simple graph and L = L(G) the Laplacian matrix of G. G is called L-integral if all its Laplacian eigenvalues are integer numbers. It is known that every cograph, a graph free of P4, is L-integral. The class of P4-sparse graphs…

Discrete Mathematics · Computer Science 2016-11-28 Renata Del-Vecchio , Atila Jones

A graph $G$ is $k$-factor-critical if $G-S$ has a perfect matching for any $k$-subset $S$ of the vertex set of $G$. In this paper, we investigate the factor-criticality of graphs with fixed minimum degree and provide sufficient conditions…

Combinatorics · Mathematics 2024-01-03 Jin Cai , Bo Zhou

We consider a Laplacian on periodic discrete graphs. Its spectrum consists of a finite number of bands. In a class of periodic 1-forms, i.e., functions defined on edges of the periodic graph, we introduce a subclass of minimal forms with a…

Spectral Theory · Mathematics 2019-05-28 E. Korotyaev , N. Saburova