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We construct the first known examples of infinite subgroups of the outer automorphism group of Out(A_Gamma), for certain right-angled Artin groups A_Gamma. This is achieved by introducing a new class of graphs, called focused graphs, whose…

Group Theory · Mathematics 2015-07-17 Corey Bregman , Neil J. Fullarton

We show that every two-term tilting complex over an Artin algebra has a tilting module over a certain factor algebra as a homology group. Also, we determine the endomorphism algebra of such a homology group, which is given as a certain…

Representation Theory · Mathematics 2011-07-01 Hiroki Abe

We study vertex-ordering problems in loop-free digraphs subject to constraints on the left-going arcs, focusing on existence conditions and computational complexity. As an intriguing special case, we explore vertex-specific lower and upper…

Combinatorics · Mathematics 2025-09-08 Nóra A. Borsik , Péter Madarasi

Chip firing provides a way to study the sandpile group (also known as the Jacobian) of a graph. We use a generalized version of chip firing to bound the number of invariant factors of the critical group of an arithmetical structure on a…

Combinatorics · Mathematics 2025-07-04 Kassie Archer , Alexander Diaz-Lopez , Darren Glass , Joel Louwsma

The result of this paper is the determination of the cohomology of Artin groups of type A_n, B_n and \tilde{A}_{n} with non-trivial local coefficients. The main result is an explicit computation of the cohomology of the Artin group of type…

Algebraic Topology · Mathematics 2007-05-23 Filippo Callegaro , Davide Moroni , Mario Salvetti

We analyse graphs in which each vertex is assigned random coordinates in a geometric space of arbitrary dimensionality and only edges between adjacent points are present. The critical connectivity is found numerically by examining the size…

Statistical Mechanics · Physics 2009-11-07 Jesper Dall , Michael Christensen

Let $W$ be a right-angled Coxeter group corresponding to a finite non-discrete graph $\mathcal{G}$ with at least $3$ vertices. Our main theorem says that $\mathcal{G}^c$ is connected if and only if for any infinite index quasiconvex…

Geometric Topology · Mathematics 2020-09-23 Michal Buran

Let $\Gamma$ be a finite graph and let $A(\Gamma)$ be the corresponding right-angled Artin group. We characterize the Hamiltonicity of $\Gamma$ via the structure of the cohomology algebra of $A(\Gamma)$. In doing so, we define and develop a…

Group Theory · Mathematics 2021-08-25 Ramón Flores , Delaram Kahrobaei , Thomas Koberda

A split graph is a graph whose vertices can be partitioned into a clique and a stable set. We investigate the combinatorial species of split graphs, providing species-theoretic generalizations of enumerative results due to B\'ina and…

Combinatorics · Mathematics 2019-07-16 Justin M. Troyka

Graph-structured data are an integral part of many application domains, including chemoinformatics, computational biology, neuroimaging, and social network analysis. Over the last two decades, numerous graph kernels, i.e. kernel functions…

Machine Learning · Computer Science 2021-03-10 Karsten Borgwardt , Elisabetta Ghisu , Felipe Llinares-López , Leslie O'Bray , Bastian Rieck

We show that problems which have finite integer index and satisfy a requirement we call treewidth-bounding admit linear kernels on the class of $H$-topological-minor free graphs, for an arbitrary fixed graph $H$. This builds on earlier…

Data Structures and Algorithms · Computer Science 2012-07-16 Alexander Langer , Felix Reidl , Peter Rossmanith , Somnath Sikdar

The semidirect product of a finitely generated group dual with the symmetric group can be described through so-called group-theoretical categories of partitions (covers only a special case; due to Raum--Weber, 2015) and skew categories of…

Quantum Algebra · Mathematics 2022-03-25 Daniel Gromada

By introducing branching conditions on the defining graph, we prove a range of rigidity results for quasiisometric embeddings between right-angled Artin groups. The starting point for these is that, under mild conditions on the codomain,…

Group Theory · Mathematics 2026-05-13 Shaked Bader , Oussama Bensaid , Harry Petyt

A graph is locally chordal if each of its small-radius balls is chordal. In an earlier work [AKK25], the authors and Kobler proved that locally chordal graphs can be characterized by having chordal local covers, by forbidding short cycles…

Combinatorics · Mathematics 2025-12-23 Tara Abrishami , Paul Knappe

We show that a locally finite, connected graph $G$ is $r$-locally chordal (that is, its $r/2$-balls are chordal) if and only if the unique canonical graph-decomposition $\mathcal{H}_r(G)$ of $G$ displaying its $r$-global structure is into…

Combinatorics · Mathematics 2026-05-05 Raphael W. Jacobs , Paul Knappe

We consider a class of growing random graphs obtained by creating vertices sequentially one by one: at each step, we choose uniformly the neighbours of the newly created vertex; its degree is a random variable with a fixed but arbitrary…

Combinatorics · Mathematics 2013-11-13 Svante Janson , Simone Severini

An arithmetical structure on a finite, connected graph without loops is given by an assignment of positive integers to the vertices such that, at each vertex, the integer there is a divisor of the sum of the integers at adjacent vertices,…

Combinatorics · Mathematics 2024-01-30 Alexander Diaz-Lopez , Joel Louwsma

We determine the image of the Artin groups of types B and D inside the Iwahori-Hecke algebras, when defined over finite fields, in the semisimple case. This generalizes earlier work on type A by Brunat, Magaard and Marin. In this…

Representation Theory · Mathematics 2017-07-11 Alexandre Esterle

We provide an explicit presentation of the automorphism group of an edge-separated CLTTF Artin group.

Group Theory · Mathematics 2022-01-10 Byung Hee An , Youngjin Cho

We prove a new version of the classical peak-reduction theorem for automorphisms of free groups in the setting of right-angled Artin groups. We use this peak-reduction theorem to prove two important corollaries about the action of the…

Group Theory · Mathematics 2014-10-01 Matthew B. Day
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