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In this paper we study the classification of right-angled Artin groups up to commensurability. We characterise the commensurability classes of RAAGs defined by trees of diameter 4. In particular, we prove a conjecture of Behrstock and…

Group Theory · Mathematics 2018-03-29 Montserrat Casals-Ruiz , Ilya Kazachkov , Alexander Zakharov

Nonlinear spectral gaps with respect to uniformly convex normed spaces are shown to satisfy a spectral calculus inequality that establishes their decay along Cesaro averages. Nonlinear spectral gaps of graphs are also shown to behave…

Metric Geometry · Mathematics 2014-09-30 Manor Mendel , Assaf Naor

We study the structure and compute the stable rank of C*-algebras of finite higher-rank graphs. We completely determine the stable rank of the C*-algebra when the k-graph either contains no cycle with an entrance, or is cofinal. We also…

Operator Algebras · Mathematics 2021-09-08 David Pask , Adam Sierakowski , Aidan Sims

A unified approach to studying convergence and stochastic stability of continuous time consensus protocols (CPs) is presented in this work. Our method applies to networks with directed information flow; both cooperative and noncooperative…

Optimization and Control · Mathematics 2012-06-05 Georgi S. Medvedev

Consider the ring $R:=\Q[\tau,\tau^{-1}]$ of Laurent polynomials in the variable $\tau$. The Artin's Pure Braid Groups (or Generalized Pure Braid Groups) act over $R,$ where the action of every standard generator is the multiplication by…

Group Theory · Mathematics 2007-05-23 Simona Settepanella

We show that formal eigenvalue equations of analytic one-frequency Schr\"od-inger operators admit intrinsic analytic $Sp(2k,\C)$ structures, where $k=k(E)$ is the T-acceleration in global theory. For trigonometric potentials those…

Spectral Theory · Mathematics 2026-03-24 Lingrui Ge , Svetlana Jitomirskaya

The aim of this paper is to study the spectral gap and the logarithmic Sobolev constant for continuous spin systems. A simple but general result for estimating the spectral gap of finite dimensional systems is given by Theorem 1.1, in terms…

Probability · Mathematics 2010-04-27 Mu-Fa Chen

We give an algorithm to compute stable commutator length in free products of cyclic groups which is polynomial time in the length of the input, the number of factors, and the orders of the finite factors. We also describe some experimental…

Geometric Topology · Mathematics 2013-04-24 Alden Walker

We consider rectangular graph superlattices of sides l1, l2 with the wavefunction coupling at the junctions either of the delta type, when they are continuous and the sum of their derivatives is proportional to the common value at the…

Condensed Matter · Physics 2016-08-31 Pavel Exner , Ralf Gawlista

Given a finite graph G there is a corresponding group given by the presentation with generators the vertices of G and a relation [x,y]=1 for generators x and y precisely when (x,y) is an edge of G. Such groups are known as partially…

Group Theory · Mathematics 2007-07-03 Andrew J Duncan , Ilya V Kazachkov , Vladimir N Remeslennikov

The fractional stable set polytope ${\rm FRAC}(G)$ of a simple graph $G$ with $d$ vertices is a rational polytope that is the set of nonnegative vectors $(x_1,\ldots,x_d)$ satisfying $x_i+x_j\le 1$ for every edge $(i,j)$ of $G$. In this…

Combinatorics · Mathematics 2018-09-03 Ginji Hamano , Takayuki Hibi , Hidefumi Ohsugi

We show that every right-angled Artin group AG defined by a graph G of finite chromatic number is poly-free with poly-free length bounded between the clique number and the chromatic number of G. Further, a characterization of all…

Group Theory · Mathematics 2007-05-23 Susan Hermiller , Zoran Sunik

One-flip stable configurations of an Ising-model on a random graph with fluctuating connectivity are examined. In order to perform the quenched average of the number of stable configurations we introduce a global order-parameter function…

Disordered Systems and Neural Networks · Physics 2009-11-07 Johannes Berg , Mauro Sellitto

We prove that a distance-regular graph with a dominant distance is a spectral expander. The key ingredient of the proof is a new inequality on the intersection numbers. We use the spectral gap bound to study the structure of the…

Combinatorics · Mathematics 2021-07-28 Bohdan Kivva

We use polyhedral product models to analyse the structure of the commutator subgroup of a right-angled Artin group. In particular, we provide a minimal set of generators for the commutator subgroup, consisting of special iterated…

Group Theory · Mathematics 2018-12-24 Taras Panov , Yakov Veryovkin

Suppose that you add rigid bars between points in the plane, and suppose that a constant fraction $q$ of the points moves freely in the whole plane; the remaining fraction is constrained to move on fixed lines called sliders. When does a…

Combinatorics · Mathematics 2015-02-23 Julien Barré , Marc Lelarge , Dieter Mitsche

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

The center $\mathscr{Z}_n(q)$ of the integral group algebra of the general linear group $GL_n(q)$ over a finite field admits a filtration with respect to the reflection length. We show that the structure constants of the associated graded…

Representation Theory · Mathematics 2019-05-14 Jinkui Wan , Weiqiang Wang

We study spectra of noncommutative dynamical systems, representations of fractal groups, and regular graphs. We explicitly compute these spectra for five examples of groups acting on rooted trees, and in three cases obtain totally…

Group Theory · Mathematics 2009-11-28 Laurent Bartholdi , Rostislav I. Grigorchuk

Finding the multiplicity of cycles in bipartite graphs is a fundamental problem of interest in many fields including the analysis and design of low-density parity-check (LDPC) codes. Recently, Blake and Lin computed the number of shortest…

Discrete Mathematics · Computer Science 2019-06-03 Ali Dehghan , Amir H. Banihashemi