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It is shown that an undirected graph $G$ is cospectral with the Hermitian adjacency matrix of a mixed graph $D$ obtained from a subgraph $H$ of $G$ by orienting some of its edges if and only if $H=G$ and $D$ is obtained from $G$ by a…

Combinatorics · Mathematics 2015-05-14 Bojan Mohar

We introduce a non-backtracking Laplace operator for graphs and we investigate its spectral properties. With the use of both theoretical and computational techniques, we show that the spectrum of this operator captures several structural…

Spectral Theory · Mathematics 2023-06-13 Jürgen Jost , Raffaella Mulas , Leo Torres

Graphs are ubiquitous in modelling relational structures. Recent endeavours in machine learning for graph-structured data have led to many architectures and learning algorithms. However, the graph used by these algorithms is often…

Machine Learning · Statistics 2020-06-25 Soumyasundar Pal , Saber Malekmohammadi , Florence Regol , Yingxue Zhang , Yishi Xu , Mark Coates

We consider the problem of clustering grouped data with possibly non-exchangeable groups whose dependencies can be characterized by a known directed acyclic graph. To allow the sharing of clusters among the non-exchangeable groups, we…

Let $X$ be bipartite mixed graph and for a unit complex number $\alpha$, $H_\alpha$ be its $\alpha$-hermitian adjacency matrix. If $X$ has a unique perfect matching, then $H_\alpha$ has a hermitian inverse $H_\alpha^{-1}$. In this paper we…

Combinatorics · Mathematics 2022-05-17 Mohammad Abudayah , Omar Alomari , Omar AbuGhneim

The topological (or graph) structures of real-world networks are known to be predictive of multiple dynamic properties of the networks. Conventionally, a graph structure is represented using an adjacency matrix or a set of hand-crafted…

Social and Information Networks · Computer Science 2016-10-21 Cheng Li , Xiaoxiao Guo , Qiaozhu Mei

We introduce a hypergraph matrix, named the unified matrix, and use it to represent the hypergraph as a graph. We show that the unified matrix of a hypergraph is identical to the adjacency matrix of the associated graph. This enables us to…

Combinatorics · Mathematics 2024-11-12 R. Vishnupriya , R. Rajkumar

We study the spectra of mixed graphs about its Hermitian adjacency matrix of the second kind (i.e. N-matrix) introduced by Mohar [1]. We extend some results and define one new Hermitian adjacency matrix, and the entry corresponding to an…

Combinatorics · Mathematics 2022-06-08 Tao She , Chunxiang Wang

We generalize classical results in spectral graph theory and linear algebra more broadly, from the case where the underlying matrix is Hermitian to the case where it is non-Hermitian. New admissibility conditions are introduced to replace…

Spectral Theory · Mathematics 2019-05-21 Edinah K. Gnang , James M. Murphy

Nikiforov\cite{nikiforov2017merging} introduced the concept of the $A_{\p}$-matrix as a convex linear combination of a graph's adjacency matrix and its diagonal matrix of vertex degrees. In this paper, we introduce a new variant of the…

Spectral Theory · Mathematics 2025-09-03 Piyush Sharma , Ravinder Kumar

In the theory of line graphs of undirected graphs there exists an important theorem linking the incidence matrix of the root graph to the adjacency matrix of its line graph. For directed or mixed graphs, however, the exists no analogous…

Combinatorics · Mathematics 2022-05-12 Mohammad Abudayah , Omar Alomari , Torsten Sander

Graph clustering aims at discovering a natural grouping of the nodes such that similar nodes are assigned to a common cluster. Many different algorithms have been proposed in the literature: for simple graphs, for graphs with attributes…

Machine Learning · Computer Science 2023-11-06 Ylli Sadikaj , Yllka Velaj , Sahar Behzadi , Claudia Plant

NodeTrix representations are a popular way to visualize clustered graphs; they represent clusters as adjacency matrices and inter-cluster edges as curves connecting the matrix boundaries. We study the complexity of constructing NodeTrix…

Computational Geometry · Computer Science 2016-09-12 Giordano Da Lozzo , Giuseppe Di Battista , Fabrizio Frati , Maurizio Patrignani

Graphs are complex objects that do not lend themselves easily to typical learning tasks. Recently, a range of approaches based on graph kernels or graph neural networks have been developed for graph classification and for representation…

Machine Learning · Computer Science 2022-05-19 Chen Cai , Yusu Wang

We completely characterize the conditions under which a complex unitary number is an eigenvalue of the non-backtracking matrix of an undirected graph. Further, we provide a closed formula to compute its geometric multiplicity and describe…

Combinatorics · Mathematics 2026-01-05 Leo Torres

We investigate the relationship between the structure of a discrete graphical model and the support of the inverse of a generalized covariance matrix. We show that for certain graph structures, the support of the inverse covariance matrix…

Machine Learning · Statistics 2014-01-07 Po-Ling Loh , Martin J. Wainwright

During routine state space circuit analysis of an arbitrarily connected set of nodes representing a lossless LC network, a matrix was formed that was observed to implicitly capture connectivity of the nodes in a graph similar to the…

Combinatorics · Mathematics 2018-03-07 Pritam Mukherjee , L. Satish

We develop the theory of linear evolution equations associated with the adjacency matrix of a graph, focusing in particular on infinite graphs of two kinds: uniformly locally finite graphs as well as locally finite line graphs. We discuss…

Dynamical Systems · Mathematics 2018-07-26 Delio Mugnolo

Matrices are two-dimensional data structures allowing one to conceptually organize information. For example, adjacency matrices are useful to store the links of a network; correlation matrices are simple ways to arrange gene co-expression…

Disordered Systems and Neural Networks · Physics 2022-09-29 Flaviano Morone

In this work, we propose a novel representation of complex multi-relational networks, which is compact and allows very efficient network analysis. Multi-relational networks capture complex data relationships and have a variety of…

Machine Learning · Computer Science 2023-05-18 Konstantinos Bougiatiotis , Georgios Paliouras