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We show that distinct topological phases of the band structure of a non-Hermitian Hamiltonian can be classified with elements of the braid group. As the proof of principle, we consider the non-Hermitian evolution of the statistics of…

Mesoscale and Nanoscale Physics · Physics 2013-05-23 Jie Ren , N. A. Sinitsyn

We show that a construction by Aanderaa and Cohen used in their proof of the Higman Embedding Theorem preserves torsion length. We give a new construction showing that every finitely presented group is the quotient of some $C'(1/6)$…

Group Theory · Mathematics 2018-09-05 Maurice Chiodo , Rishi Vyas

We give a new proof of the absence of non-trivial idempotents in the group ring of torsion-free cocompact lattices in SL(n,C). It is based on the following procedure. We lift the class of the trace in the cyclic cohomology of the group ring…

K-Theory and Homology · Mathematics 2007-06-18 Mathias Fuchs

We construct uncountably many finitely generated, pairwise non-isomorphic torsion-free groups, all of which fall into the same quasi-isometry class. This is done by considering Schur covering groups and group cohomology, with the necessary…

Group Theory · Mathematics 2025-11-19 Vladimir Vankov

Using totally symmetric sets, Chudnovsky, Kordek, Li, and Partin gave a superexponential lower bound on the cardinality of non-abelian finite quotients of the braid group. In this paper, we develop new techniques using multiple totally…

Group Theory · Mathematics 2021-04-07 Nancy Scherich , Yvon Verberne

Let G be the fundamental group of the complement of a K(G,1) hyperplane arrangement (such as Artin's pure braid group) or more generally a homologically toroidal group (as defined in the paper). The subgroup of elements in the complex…

Algebraic Topology · Mathematics 2007-05-23 Alejandro Adem , Daniel C. Cohen , Frederick R. Cohen

In 2002 Polterovich has notably established that on closed aspherical symplectic manifolds, Hamiltonian diffeomorphisms of finite order, which we call Hamiltonian torsion, must in fact be trivial. In this paper we prove the first…

Symplectic Geometry · Mathematics 2020-09-09 Marcelo S. Atallah , Egor Shelukhin

We give a complete characterization of torsion-free hyperbolic groups which are homogeneous in the sense of first-order logic, in terms of the JSJ decompositions of their free factors.

Group Theory · Mathematics 2019-07-09 Ayala Dente-Byron , Chloé Perin

The deep connection among braids, knots and topological physics has provided valuable insights into studying topological states in various physical systems. However, identifying distinct braid groups and knot topology embedded in…

Mesoscale and Nanoscale Physics · Physics 2024-08-06 Jiangzhi Chen , Zi Wang , Yu-Tao Tan , Ce Wang , Jie Ren

The Resolution Theorem for Compact Abelian Groups is applied to show that the profinite subgroups of a finite-dimensional compact connected abelian group (protorus) which induce tori quotients comprise a lattice under intersection (meet)…

Group Theory · Mathematics 2025-03-28 Wayne Lewis

In this note we prove the claim given in the title. A group G is noncommutatively slender if each map from the fundamental group of the Hawaiian Earring to G factors through projection to a canonical free subgroup. Graham Higman, in his…

Group Theory · Mathematics 2019-08-13 Samuel M. Corson

We revisit the problem of classifying topological band structures in non-Hermitian systems. Recently, a solution has been proposed, which is based on redefining the notion of energy band gap in two different ways, leading to the so-called…

Mathematical Physics · Physics 2020-05-20 Charles C. Wojcik , Xiao-Qi Sun , Tomáš Bzdušek , Shanhui Fan

We continue the study of freely braided elements of simply laced Coxeter groups, which we introduced in a previous work (math.CO/0301104). A known upper bound for the number of commutation classes of reduced expressions for an element of a…

Combinatorics · Mathematics 2007-05-23 R. M. Green , J. Losonczy

We prove by explicit construction that graph braid groups and most surface groups can be embedded in a natural way in right-angled Artin groups, and we point out some consequences of these embedding results. We also show that every…

Group Theory · Mathematics 2014-10-01 John Crisp , Bert Wiest

We reduce a strong version of the twist conjecture for Artin groups to Artin groups whose defining graphs have no separating vertices. This produces new examples of Artin groups satisfying the conjecture, and sheds more light on the…

Group Theory · Mathematics 2026-05-13 Oli Jones , Giorgio Mangioni , Giovanni Sartori

We show that braid groups with at most 6 strands are CAT(0) using the close connection between these groups, the associated non-crossing partition complexes and the embeddability of their diagonal links into spherical buildings of type A.…

Group Theory · Mathematics 2016-09-01 Thomas Haettel , Dawid Kielak , Petra Schwer

We define an integer-valued invariant of special cube complexes called the genus, and prove that having genus one characterizes special cube complexes with abelian fundamental group. Using the genus, we obtain a new proof that the…

Geometric Topology · Mathematics 2016-12-30 Corey Bregman

We study a subset of square free positive braids and we give a few algebraic characterizations of them and one geometric characterization: the set of positive braids whose closures are unlinks. We describe canonical forms of these braids…

Geometric Topology · Mathematics 2010-04-01 Rehana Ashraf , Barbu Berceanu

We introduce a notion of "freely braided element" for simply laced Coxeter groups. We show that an arbitrary group element $w$ has at most $2^{N(w)}$ commutation classes of reduced expressions, where $N(w)$ is a certain statistic defined in…

Combinatorics · Mathematics 2007-05-23 R. M. Green , J. Losonczy

We construct a non-free but aleph_1-separable, torsion-free abelian group G with a pure free subgroup B such that all subgroups of G disjoint from B are free and such that G/B is divisible. This answers a question of Irwin and shows that a…

Logic · Mathematics 2007-11-21 Andreas Blass , Saharon Shelah