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To each graph on $n$ vertices there is an associated subspace of the $n \times n$ matrices called the operator system of the graph. We prove that two graphs are isomorphic if and only if their corresponding operator systems are unitally…

Operator Algebras · Mathematics 2014-12-23 Carlos M. Ortiz , Vern I. Paulsen

We present a new approach to graph limit theory which unifies and generalizes the two most well developed directions, namely dense graph limits (even the more general $L^p$ limits) and Benjamini--Schramm limits (even in the stronger…

Combinatorics · Mathematics 2018-11-05 Agnes Backhausz , Balazs Szegedy

We study analytic properties of graph product of finite groups with a hyperbolic defining graph. This is done by studying dynamics on the Bowditch compactification of the extension graph, or the crossing graph, of graph product. In…

Group Theory · Mathematics 2024-12-25 Koichi Oyakawa

We determine the structure of automorphism groups of finite graphs of bounded Hadwiger number. Our proof includes a structural analysis of finite edge-transitive graphs. In particular, we show that for connected, $K_{h+1}$-minor-free,…

Combinatorics · Mathematics 2025-09-24 Martin Grohe , Pascal Schweitzer , Daniel Wiebking

We consider selfadjoint operators obtained by pasting a finite number of boundary relations with one-dimensional boundary space. A typical example of such an operator is the Schr\"odinger operator on a star-graph with a finite number of…

Spectral Theory · Mathematics 2023-10-17 Sergey Simonov , Harald Woracek

In this paper we define a way to get a bounded invertible automaton starting from a finite graph. It turns out that the corresponding automaton group is regular weakly branch over its commutator subgroup, contains a free semigroup on two…

Group Theory · Mathematics 2021-06-10 Matteo Cavaleri , Daniele D'Angeli , Alfredo Donno , Emanuele Rodaro

We analyze properties of semigroups generated by Schr\"odinger operators $-\Delta+V$ or polyharmonic operators $-(-\Delta)^m$, on metric graphs both on $L^p$-spaces and spaces of continuous functions. In the case of spatially constant…

Spectral Theory · Mathematics 2020-12-11 Simon Becker , Federica Gregorio , Delio Mugnolo

On finite metric graphs we consider Laplace operators, subject to various classes of non-self-adjoint boundary conditions imposed at graph vertices. We investigate spectral properties, existence of a Riesz basis of projectors and similarity…

Spectral Theory · Mathematics 2021-03-30 Amru Hussein , David Krejcirik , Petr Siegl

Here we introduce connectivity operators, namely, diffusion operators, general Laplacian operators, and general adjacency operators for hypergraphs. These operators are generalisations of some conventional notions of apparently different…

Combinatorics · Mathematics 2023-06-22 Anirban Banerjee , Samiron Parui

We study weighted composition operators on Hilbert spaces of analytic functions on the unit ball with kernels of the form $(1-<z,w>)^{-\gamma}$ for $\gamma>0$. We find necessary and sufficient conditions for the adjoint of a weighted…

Functional Analysis · Mathematics 2012-07-26 Trieu Le

In this paper, we will compute the moments of the block operators, induced by the generators of the group, in a group von Neumann algebra and we will observe the identically distributedness.

Operator Algebras · Mathematics 2007-05-23 Ilwoo Cho

We provide criteria for self-adjointness and {\tau}-Fredhomness of first and second order differential operators acting on sections of infinite dimensional bundles, whose fibers are modules of finite type over a von Neumann algebra A…

Operator Algebras · Mathematics 2015-12-01 Maxim Braverman , Simone Cecchini

In this article, we aim to provide a satisfactory algebraic description of the set of affiliated operators for von Neumann algebras. Let $\mathscr{M}$ be a von Neumann algebra acting on a Hilbert space $\mathcal{H}$, and let…

Operator Algebras · Mathematics 2024-10-03 Indrajit Ghosh , Soumyashant Nayak

A one-by-one exhaustion is a combinatorial/geometric condition which excludes eigenvalues from the spectra of Laplace and Schr\"odinger operators on graphs. Isoperimetric inequalities in graphs with a cocompact automorphism group provide an…

Spectral Theory · Mathematics 2022-12-29 Rostislav Grigorchuk , Christophe Pittet

In this expository paper we answer two fundamental questions concerning discrete magnetic Schr\"odinger operator associated with weighted graphs. We discuss when formal expressions of such operators give rise to self-adjoint operators,…

Functional Analysis · Mathematics 2018-05-23 Marcel Schmidt

Using the recent theory of Krein--von Neumann extensions for positive functionals we present several simple criteria to decide whether a given positive functional on the full operator algebra is normal. We also characterize those…

Functional Analysis · Mathematics 2017-10-19 Zoltán Sebestyén , Zsigmond Tarcsay , Tamás Titkos

A theory of orientation on gain graphs (voltage graphs) is developed to generalize the notion of orientation on graphs and signed graphs. Using this orientation scheme, the line graph of a gain graph is studied. For a particular family of…

Combinatorics · Mathematics 2015-06-17 Nathan Reff

We study Laplacians associated to a graph and single out a class of such operators with special regularity properties. In the case of locally finite graphs, this class consists of all selfadjoint, non-negative restrictions of the standard…

Functional Analysis · Mathematics 2013-05-07 Sebastian Haeseler , Matthias Keller , Daniel Lenz , Radosław Wojciechowski

The idea of graph compositions, which was introduced by A. Knopfmacher and M. E. Mays, generalizes both ordinary compositions of positive integers and partitions of finite sets. In their original paper they developed formulas, generating…

Combinatorics · Mathematics 2007-05-23 Aminul Huq

Graph products for groups were defined by Green in her thesis as a generalization of both Cartesian and free products. In this paper we define the corresponding graph product for reduced and maximal C*-algebras, von Neumann algebras and…

Operator Algebras · Mathematics 2020-02-17 Martijn Caspers , Pierre Fima