scholarly journals AUTOMATIC STRUCTURES AND BOUNDARIES FOR GRAPHS OF GROUPS

1994 ◽  
Vol 04 (04) ◽  
pp. 591-616 ◽  
Author(s):  
WALTER D. NEUMANN ◽  
MICHAEL SHAPIRO
Keyword(s):  
Fundamental Group ◽  
Equivalence Relation ◽  
Infinite Product ◽  
Graph Product ◽  
Graph Of Groups ◽  
Automatic Structures ◽  
Graphs Of Groups ◽  
Underlying Graph ◽  
Edge Group ◽  
Labelled Graphs

We study the synchronous and asynchronous automatic structures on the fundamental group of a graph of groups in which each edge group is finite. Up to a natural equivalence relation, the set of biautomatic structures on such a graph product bijects to the product of the sets of biautomatic structures on the vertex groups. The set of automatic structures is much richer. Indeed, it is dense in the infinite product of the sets of automatic structures of all conjugates of the vertex groups. We classify these structures by a class of labelled graphs which “mimic” the underlying graph of the graph of groups. Analogous statements hold for asynchronous automatic structures. We also discuss the boundaries of these structures.

AUTOMATIC STRUCTURES FOR FUNDAMENTAL GROUPOIDS OF GRAPHS OF GROUPS

2005 ◽  
Vol 15 (01) ◽  
pp. 129-142
Author(s):  
PAUL LUNAU
Keyword(s):  
Free Product ◽  
Sufficient Conditions ◽  
Graph Of Groups ◽  
Automatic Structures ◽  
Graphs Of Groups ◽  
Free Product With Amalgamation ◽  
Fundamental Groupoid

We give sufficient conditions for the fundamental groupoid of a graph of groups to be automatic (resp. asynchronously automatic). These conditions are similar to those in [1] for a free product with amalgamation to be automatic (resp. asynchronously automatic).

scholarly journals $C^*$-algebras associated with the fundamental groups of graphs of groups

2005 ◽  
Vol 97 (1) ◽  
pp. 49 ◽  
Author(s):  
Rui Okayasu
Keyword(s):  
Fundamental Group ◽  
Hyperbolic Group ◽  
Fundamental Groups ◽  
Graph Of Groups ◽  
C Algebra ◽  
C Algebras ◽  
Graphs Of Groups ◽  
Word Hyperbolic Group ◽  
Dimensional Boundary ◽  
The Ideal

We construct a nuclear $C^*$-algebra associated with the fundamental group of a graph of groups of finite type. It is well-known that every word-hyperbolic group with zero-dimensional boundary, in other words, every group acting trees with finite stabilizers is given by the fundamental group of such a graph of groups. We show that our $C^*$-algebra is $*$-isomorphic to the crossed product arising from the associated boundary action and is also given by a Cuntz-Pimsner algebra. We also compute the K-groups and determine the ideal structures of our $C^*$-algebras.

scholarly journals Graphical splittings of Artin kernels

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Enrique Miguel Barquinero ◽  
Lorenzo Ruffoni ◽  
Kaidi Ye
Keyword(s):  
Free Group ◽  
Artin Group ◽  
Artin Groups ◽  
Graphs Of Groups ◽  
Underlying Graph ◽  
Block Graphs ◽  
Right Angled Artin Groups

Abstract We study Artin kernels, i.e. kernels of discrete characters of right-angled Artin groups, and we show that they decompose as graphs of groups in a way that can be explicitly computed from the underlying graph. When the underlying graph is chordal, we show that every such subgroup either surjects to an infinitely generated free group or is a generalized Baumslag–Solitar group of variable rank. In particular, for block graphs (e.g. trees), we obtain an explicit rank formula and discuss some features of the space of fibrations of the associated right-angled Artin group.

scholarly journals A criterion for residual 𝑝-finiteness of arbitrary graphs of finite 𝑝-groups

2019 ◽  
Vol 22 (5) ◽  
pp. 837-844
Author(s):  
Gareth Wilkes
Keyword(s):  
Fundamental Group ◽  
Infinite Graphs ◽  
Graphs Of Groups ◽  
Arbitrary Graphs

Abstract We establish conditions under which the fundamental group of a graph of finite p-groups is necessarily residually p-finite. The technique of proof is independent of previously established results of this type, and the result is also valid for infinite graphs of groups.

FIXED POINTS OF SYMMETRIC ENDOMORPHISMS OF GROUPS

2002 ◽  
Vol 12 (05) ◽  
pp. 737-745 ◽  
Author(s):  
MIHALIS SYKIOTIS
Keyword(s):  
Fundamental Group ◽  
Fixed Points ◽  
Structure Theorem ◽  
Graph Of Groups

Let G be the fundamental group of a graph of groups with finite edge groups and f an endomorphism of G. We prove a structure theorem for the subgroup Fix(f), which consists of the elements of G fixed by f, in the case where the endomorphism f of G maps vertex groups into conjugates of themselves.

THE COMBINATION THEOREM AND QUASICONVEXITY

2001 ◽  
Vol 11 (02) ◽  
pp. 185-216 ◽  
Author(s):  
ILYA KAPOVICH
Keyword(s):  
Fundamental Group ◽  
Isometric Embedding ◽  
Normal Forms ◽  
Vertex Group ◽  
Graph Of Groups

We show that if G is a fundamental group of a finite k-acylindrical graph of groups where every vertex group is word-hyperbolic and where every edge-monomorphism is a quasi-isometric embedding, then all the vertex groups are quasiconvex in G (the group G is word-hyperbolic by the Combination Theorem of M. Bestvina and M. Feighn). This allows one, in particular, to approximate the word metric on G by normal forms for this graph of groups.

DETERMINISTIC AND NON-DETERMINISTIC ASYNCHRONOUS AUTOMATIC STRUCTURES

1992 ◽  
Vol 02 (03) ◽  
pp. 297-305 ◽  
Author(s):  
MICHAEL SHAPIRO
Keyword(s):  
Equivalence Relation ◽  
Automatic Structures ◽  
Fellow Traveller ◽  
Automatic Structure ◽  
Definition Of ◽  
Fellow Traveller Property

Following the definition of asynchronous automatic structures in [3], we define non-deterministic asynchronous automatic structures and characterize these in terms of the asynchronous fellow traveller property. We show that any group with a non-deterministic asynchronous automatic structure has an asynchronous automatic structure. Non-deterministic asynchronous automatic structures are a labor saving method of showing that a group has an asynchronous automatic structure. They also allow one to define an equivalence relation on the class of non-deterministic asynchronous automatic structures which descends to the subclasses of deterministic asynchronous automatic structures and synchronous automatic structures.

scholarly journals Isometric embeddings in bounded cohomology

2014 ◽  
Vol 06 (01) ◽  
pp. 1-25 ◽  
Author(s):  
M. Bucher ◽  
M. Burger ◽  
R. Frigerio ◽  
A. Iozzi ◽  
C. Pagliantini ◽  
...  
Keyword(s):  
Fundamental Group ◽  
Isometric Embedding ◽  
Equivalence Theorem ◽  
Connected Component ◽  
Bounded Cohomology ◽  
Graph Of Groups ◽  
Simplicial Volume ◽  
Direct Sum ◽  
Isometric Embeddings ◽  
Relative Bounded Cohomology

This paper is devoted to the construction of norm-preserving maps between bounded cohomology groups. For a graph of groups with amenable edge groups, we construct an isometric embedding of the direct sum of the bounded cohomology of the vertex groups in the bounded cohomology of the fundamental group of the graph of groups. With a similar technique we prove that if (X, Y) is a pair of CW-complexes and the fundamental group of each connected component of Y is amenable, the isomorphism between the relative bounded cohomology of (X, Y) and the bounded cohomology of X in degree at least 2 is isometric. As an application we provide easy and self-contained proofs of Gromov's Equivalence Theorem and of the additivity of the simplicial volume with respect to gluings along π1-injective boundary components with amenable fundamental group.

ON RESIDUAL FINITENESS OF GRAPHS OF NILPOTENT GROUPS

2004 ◽  
Vol 14 (04) ◽  
pp. 403-408
Author(s):  
E. RAPTIS ◽  
O. TALELLI ◽  
D. VARSOS
Keyword(s):  
Finite Groups ◽  
Finite Graph ◽  
Nilpotent Groups ◽  
Fundamental Groups ◽  
Residual Finiteness ◽  
Graph Of Groups ◽  
Residually Finite ◽  
Edge Group ◽  
Residually Finite Groups ◽  
Torsion Free

Here we characterize the residually finite groups G which are the fundamental groups of a finite graph of finitely generated torsion-free nilpotent groups. Namely we show that G is residually finite if and only if for each edge group of the graph of groups the two edge monomorphisms differ essentially by an isomorphism of certain subgroups of the Mal'cev completion of the corresponding vertex groups.

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