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Finite-finitary, polycyclic-finitary and Chernikov-finitary automorphism groups

B. A. F. Wehrfritz (2015)

Colloquium Mathematicae

If X is a property or a class of groups, an automorphism ϕ of a group G is X-finitary if there is a normal subgroup N of G centralized by ϕ such that G/N is an X-group. Groups of such automorphisms for G a module over some ring have been very extensively studied over many years. However, for groups in general almost nothing seems to have been done. In 2009 V. V. Belyaev and D. A. Shved considered the general case for X the class of finite groups. Here we look further at the finite case but our main...

Finiteness Theorems for Deformations of Complexes

Frauke M. Bleher, Ted Chinburg (2013)

Annales de l’institut Fourier

We consider deformations of bounded complexes of modules for a profinite group G over a field of positive characteristic. We prove a finiteness theorem which provides some sufficient conditions for the versal deformation of such a complex to be represented by a complex of G -modules that is strictly perfect over the associated versal deformation ring.

Fixed points for positive permutation braids

Michał Misiurewicz, Ana Rodrigues (2012)

Fundamenta Mathematicae

Making use of the Nielsen fixed point theory, we study a conjugacy invariant of braids, which we call the level index function. We present a simple algorithm for computing it for positive permutation cyclic braids.

Fixed points of endomorphisms of certain free products

Pedro V. Silva (2012)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

The fixed point submonoid of an endomorphism of a free product of a free monoid and cyclic groups is proved to be rational using automata-theoretic techniques. Maslakova’s result on the computability of the fixed point subgroup of a free group automorphism is generalized to endomorphisms of free products of a free monoid and a free group which are automorphisms of the maximal subgroup.

Fixed points of endomorphisms of certain free products

Pedro V. Silva (2012)

RAIRO - Theoretical Informatics and Applications

The fixed point submonoid of an endomorphism of a free product of a free monoid and cyclic groups is proved to be rational using automata-theoretic techniques. Maslakova’s result on the computability of the fixed point subgroup of a free group automorphism is generalized to endomorphisms of free products of a free monoid and a free group which are automorphisms of the maximal subgroup.

Folner sets of alternate directed groups

Jérémie Brieussel (2014)

Annales de l’institut Fourier

An explicit family of Folner sets is constructed for some directed groups acting on a rooted tree of sublogarithmic valency by alternate permutations. In the case of bounded valency, these groups were known to be amenable by probabilistic methods. The present construction provides a new and independent proof of amenability, using neither random walks, nor word length.

Fractal representation of the attractive lamination of an automorphism of the free group

Pierre Arnoux, Valérie Berthé, Arnaud Hilion, Anne Siegel (2006)

Annales de l’institut Fourier

In this paper, we extend to automorphisms of free groups some results and constructions that classically hold for morphisms of the free monoid, i.e., the so-called substitutions. A geometric representation of the attractive lamination of a class of automorphisms of the free group (irreducible with irreducible powers (iwip) automorphisms) is given in the case where the dilation coefficient of the automorphism is a unit Pisot number. The shift map associated with the attractive symbolic lamination...

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