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It is undecidable in general whether a given finitely presented group is word hyperbolic. We use the concept of pregroups, introduced by Stallings, to define a new class of van Kampen diagrams, which represent groups as quotients of…

We give lower bounds on the complexity of the word problem of certain non-solvable groups: for a large class of non-solvable infinite groups, including in particular free groups, Grigorchuk's group and Thompson's groups, we prove that their…

Group Theory · Mathematics 2020-06-23 Laurent Bartholdi , Michael Figelius , Markus Lohrey , Armin Weiß

The computational complexity of the word problem in HNN-extension of groups is studied. HNN-extension is a fundamental construction in combinatorial group theory. It is shown that the word problem for an ascending HNN-extension of a group H…

Group Theory · Mathematics 2021-07-06 Markus Lohrey

The isomorphism problem for infinite finitely presented groups is probably the hardest among standard algorithmic problems in group theory. Classes of groups where it has been completely solved are nilpotent groups, hyperbolic groups, and…

Group Theory · Mathematics 2025-06-18 Vladimir Shpilrain

We introduce and study the bounded word problem and the precise word problem for groups given by means of generators and defining relations. For example, for every finitely presented group, the bounded word problem is in NP, i.e., it can be…

Group Theory · Mathematics 2018-01-03 Sergei V. Ivanov

The orbit problem is at the heart of symmetry reduction methods for model checking concurrent systems. It asks whether two given configurations in a concurrent system (represented as finite strings over some finite alphabet) are in the same…

Computational Complexity · Computer Science 2015-11-17 Anthony Widjaja Lin , Sanming Zhou

One of the most interesting questions about a group is if its word problem can be solved and how. The word problem in the braid group is of particular interest to topologists, algebraists and geometers, and is the target of intensive…

Group Theory · Mathematics 2007-05-23 David Garber , Shmuel Kaplan , Mina Teicher

This paper looks at the class of groups admitting normal forms for which the right multiplication by a group element is computed in linear time on a multi-tape Turing machine. We show that the groups $\mathbb{Z}_2 \wr \mathbb{Z}^2$,…

Group Theory · Mathematics 2024-04-10 Prohrak Kruengthomya , Dmitry Berdinsky

The braid group has recently attracted much attention. This is primarily based upon the discovery of its usage in various cryptosystems [AAG],[KLCHKP]. One major focus of current research has been in solving decision problems in braid…

Group Theory · Mathematics 2007-05-23 Elie Feder

We show that the word problem for any 3-manifold group is solvable in time $O(n\log^3 n)$. Our main contribution is the proof that the word problem for admissible graphs of groups, in the sense of Croke and Kleiner, is solvable in $O(n\log…

Group Theory · Mathematics 2026-01-16 Alessandro Sisto , Stefanie Zbinden

In this paper we investigate the word problem of the free Burnside semigroup satisfying x^2=x^3 and having two generators. Elements of this semigroup are classes of equivalent words. A natural way to solve the word problem is to select a…

Formal Languages and Automata Theory · Computer Science 2011-02-22 A. N. Plyushchenko , A. M. Shur

The Equation Problem in finitely presented groups asks if there exists an algorithm which determines in finite amount of time whether any given equation system has a solution or not. We show that the Equation Problem in central extensions…

Group Theory · Mathematics 2013-07-24 Hao Liang

We analyze the proof by Lehnert and Schweitzer that the word problem of the Thompson group V is co-context-free, and we show that this word problem is the complement of the cyclic closure of a union of reverse deterministic context-free…

Group Theory · Mathematics 2025-09-10 J. C. Birget

It is shown that for graph groups (right-angled Artin groups) the conjugacy problem as well as a restricted version of the simultaneous conjugacy problem can be solved in polynomial time even if input words are represented in a compressed…

Group Theory · Mathematics 2010-03-08 Niko Haubold , Markus Lohrey , Christian Mathissen

The study of word hyperbolic groups is a prominent topic in geometric group theory; however word hyperbolic groups are defined by a geometric condition which does not extend naturally to semigroups. We propose a linguistic definition.…

Group Theory · Mathematics 2007-05-23 Andrew Duncan , Robert H. Gilman

We show that the conjugacy problem is solvable in [finitely generated free]-by-cyclic groups, by using a result of O. Maslakova that one can algorithmically find generating sets for the fixed subgroups of free group automorphisms, and one…

Group Theory · Mathematics 2007-05-23 O. Bogopolski , A. Martino , O. Maslakova , E. Ventura

We show that the compressed word problem in a finitely-generated fully residually free group (F -group) is decidable in polynomial time, and use the result to show that the word problem in the automorphism group of such a group is decidable…

Group Theory · Mathematics 2009-10-21 Jeremy Macdonald

In this survey, we address the worst-case, average-case, and generic-case time complexity of the word problem and some other algorithmic problems in several classes of groups and show that it is often the case that the average-case…

Group Theory · Mathematics 2024-01-18 Vladimir Shpilrain

We describe a procedure which verifies that a group given by generators and relators is word-hyperbolic. This procedure always works with a group which is word-hyperbolic, provided there is sufficient memory and time devoted to the problem.…

Group Theory · Mathematics 2007-05-23 David B. A. Epstein , Derek F. Holt

We begin by establishing two fundamental results on standard parabolic subgroups of virtual Artin groups. We first show that a standard parabolic subgroup is naturally isomorphic to a virtual Artin group. Second, we prove that the…

Group Theory · Mathematics 2026-03-02 José Gálvez Mateos , Federica Gavazzi , Luis Paris