arXiv subjects

Vladimir N. Remeslennikov

Publications and source records attributed to Vladimir N. Remeslennikov.

12 recordsLinked to original sources

arXiv2017

Automorphisms of Partially Commutative Groups III: Inversions and Transvections

The structure of a certain subgroup $S$ of the automorphism group of a partially commutative group (RAAG) $G$ is described in detail: namely the subgroup generated by inversions and elementary transvections. We define admissible subsets of the generators of $G$, and show that $S$ is the subgroup of automorphisms which fix all subgroups $\langle Y\rangle$ of $G$, for all admissible subsets $Y$. A decomposition of $S$ as an iterated tower of semi-direct products in given and the structure of the factors of this decomposition described. The construction allows a presentation of $S$ to be computed, from the commutation graph of $G$.

math.GR↗

arXiv2016

Measuring cones and other thick subsets in free groups

In this paper we investigate the special automata over finite rank free groups and estimate asymptotic characteristics of sets they accept. We show how one can decompose an arbitrary regular subset of a finite rank free group into disjoint union of sets accepted by special automata or special monoids. These automata allow us to compute explicitly generating functions, $λ-$measures and Cesaro measure of thick monoids. Also we improve the asymptotic classification of regular subsets in free groups.

math.GR↗

arXiv2013

Double cosets in free groups

In this paper we study double cosets of finite rank free groups. We focus our attention on cancellation types in double cosets and their formal language properties.

math.GR↗

arXiv2012

Automorphisms of Partially Commutative Groups II: Combinatorial Subgroups

We define several "standard" subgroups of the automorphism group Aut(G) of a partially commutative (right-angled Artin) group and use these standard subgroups to describe decompositions of Aut(G). If C is the commutation graph of G, we show how Aut(G) decomposes in terms of the connected components of C: obtaining a particularly clear decomposition theorem in the special case where C has no isolated vertices. If C has no vertices of a type we call dominated then we give a semi-direct decompostion of Aut(G) into a subgroup of locally conjugating automorphisms by the subgroup stabilising a certain lattice of "admissible subsets" of the vertices of C. We then characterise those graphs for which Aut(G) is a product (not necessarily semi-direct) of two such subgroups.

math.GR↗

arXiv2011

Amalgamated Products of Groups II: Measures of Random Normal Forms

Let $G=\mathop{A\ast B}\limits_C$ be an amalgamated product of finite rank free groups $A$, $B$ and $C$. We introduce atomic measures and corresponding asymptotic densities on a set of normal forms of elements in $G$. We also define two strata of normal forms: the first one consists of regular (or stable) normal forms, and second stratum is formed by singular (or unstable) normal forms. In a series of previous work about classical algorithmic problems, it was shown that standard algorithms work fast on elements of the first stratum and nothing is known about their work on the second stratum. In main theorems A and B of this paper we give probabilistic and asymptotic estimates of these strata.

math.GR↗

arXiv2009

Regular sets and counting in free groups

In this paper we study asymptotic behavior of regular subsets in a free group F of finite rank, compare their sizes at infinity, and develop techniques to compute the probabilities of sets relative to distributions on F that come naturally from no-return random walks on the Cayley graph of F. We apply these techniques to study cosets, double cosets, and Schreier representatives of finitely generated subgroups of F and also to analyze relative sizes of regular prefixed-closed subsets in F.

math.GR↗

arXiv2009

The Conjugacy Problem in Amalgamated Products I: Regular Elements and Black Holes

We discuss the time complexity of the word and conjugacy search problems for free products $G = A \star_C B$ of groups $A$ and $B$ with amalgamation over a subgroup $C$. We stratify the set of elements of $G$ with respect to the complexity of the word and conjugacy problems and show that for the generic stratum the conjugacy search problem is decidable under some reasonable assumptions about groups $A,B,C$.

math.GR↗

arXiv2009

Generic complexity of the Conjugacy Problem in HNN-extensions and algorithmic stratification of Miller's groups

We discuss time complexity of The Conjugacy Problem in HNN-extensions of groups, in particular, in Miller's groups. We show that for "almost all", in some explicit sense, elements, the Conjugacy Problem is decidable in cubic time. It is worth noting that the Conjugacy Problem in a Miller group may have be undecidable. Our results show that "hard" instances of the problem comprise a negligibly small part of the group.

math.GR↗

arXiv2008

Automorphisms of Partially Commutative Groups I: Linear Subgroups

The goal of this paper is to construct and describe certain arithmetic subgroups of the automorphism group of a partially commutative group. More precisely, given an arbitrary finite graph $Γ$ we construct an arithmetic subgroup $St(L(G))$, represented as a subgroup of $GL(n,Z)$, where $n$ is the number of vertices of the graph $Γ$. In the last section of the paper we give a description of the decomposition of the group of automorphisms $St^{conj}(L(G))$ as a semidirect product of the group of conjugating automorphisms $Conj(G)$ and $St(L(G))$. This result is closely related to Theorem 1.4 of the paper arXiv:0710.2573v1.

math.GR↗

arXiv2007

Comparison of the Discrete and Continuous Cohomology Groups of a Pro-$p$ Group

We address the following question. For which finitely generated pro-$p$ groups the comparison map $ϕ^2:H_{cont}^{2}(P,\F_p) \to H_{disc}{2}(P,\F_p)$ is an isomorphism? We prove that if $P$ is not finitely presented then $ϕ^2$ is not surjective. Furthermore, if $P$ is finitely presented $ϕ^2$ is an isomorphism if and only if the comparison map $ϕ_2:H^{disc}_{2}(P, \F_p) \to H^{cont}_{2}(P, \F_p)$ of second homology groups is an isomorphism. This is the content of Theorem A. The second main result of the paper is Theorem B, which gives an explicit construction of a cochain from the kernel of $ϕ^2$.

math.GR↗

arXiv2007

Centraliser Dimension of Partially Commutative Groups

In a previous paper we investigated the centraliser dimension of groups. In the current paper we study properties of centraliser dimension for the class of free partially commutative groups and, as a corollary, we obtain an efficient algorithm for computation of centraliser dimension in these groups.

math.GR↗

arXiv2002

Multiplicative measures on free groups

We introduce a family of atomic measures on free groups generated by no-return random walks. These measures are shown to be very convenient for comparing "relative sizes" of subgroups, context-free and regular subsets (that, subsets generated by finite automata) of free groups. Many asymptotic characteristics of subsets and subgroups are naturally expressed as analytic properties of related generating functions. We introduce an hierarchy of asymptotic behaviour "at infinity" of subsets in the free groups, more sensitive than the traditionally used asymptotic density, and apply it to normal subgroups and regular subsets.

math.GR↗