scholarly journals On growth of homology torsion in amenable groups

2016 ◽  
Vol 162 (2) ◽  
pp. 337-351 ◽  
Author(s):  
ADITI KAR ◽  
PETER KROPHOLLER ◽  
NIKOLAY NIKOLOV
Keyword(s):  
Simplicial Complex ◽  
Amenable Group ◽  
Solvable Groups ◽  
Integral Homology ◽  
Amenable Groups ◽  
Derived Length ◽  
Compact Quotient ◽  
Simply Connected

AbstractSuppose an amenable group G is acting freely on a simply connected simplicial complex $\~{X}$ with compact quotient X. Fix n ≥ 1, assume $H_n(\~{X}, \mathbb{Z}) = 0$ and let (Hi) be a Farber chain in G. We prove that the torsion of the integral homology in dimension n of $\~{X}/H_i$ grows subexponentially in [G : Hi]. This fails if X is not compact. We provide the first examples of amenable groups for which torsion in homology grows faster than any given function. These examples include some solvable groups of derived length 3 which is the minimal possible.

scholarly journals Homological dimension of elementary amenable groups

2020 ◽  
Vol 2020 (766) ◽  
pp. 45-60
Author(s):  
Peter H. Kropholler ◽  
Conchita Martínez-Pérez
Keyword(s):  
Simple Group ◽  
Characteristic Zero ◽  
Amenable Group ◽  
Solvable Groups ◽  
Complete Information ◽  
Homological Dimension ◽  
Important Paper ◽  
Amenable Groups ◽  
Coefficient Ring ◽  
Special Case

AbstractIn this paper we prove that the homological dimension of an elementary amenable group over an arbitrary commutative coefficient ring is either infinite or equal to the Hirsch length of the group. Established theory gives simple group theoretical criteria for finiteness of homological dimension and so we can infer complete information about this invariant for elementary amenable groups. Stammbach proved the special case of solvable groups over coefficient fields of characteristic zero in an important paper dating from 1970.

scholarly journals Elementary amenable groups of finite hirsch length are locally-finite by virtually-solvable

1992 ◽  
Vol 52 (2) ◽  
pp. 237-241 ◽  
Author(s):  
J. A. Hillman ◽  
P. A. Linnell
Keyword(s):  
Normal Subgroup ◽  
Amenable Group ◽  
Locally Finite ◽  
Amenable Groups ◽  
Derived Length

AbstractIf G is an elementary amenable group of finite Hirsch length h, then the quotient of G by its maximal locally finite normal subgroup has a maximal solvable normal subgroup, of derived length and index bounded in terms of h.

scholarly journals ELEMENTARY AMENABLE SUBGROUPS OF R. THOMPSON'S GROUP F

2005 ◽  
Vol 15 (04) ◽  
pp. 619-642 ◽  
Author(s):  
MATTHEW G. BRIN
Keyword(s):  
Piecewise Linear ◽  
Amenable Group ◽  
Solvable Groups ◽  
Amenable Groups ◽  
Elementary Class ◽  
Limit Ordinal ◽  
Thompson’S Group ◽  
Thompson's Group F

We study the subgroups of R. J. Thompson's group F and PLo(I), the group of orientation preserving, piecewise linear self homeomorphisms of [0, 1]. We exhibit, for each non-limit ordinal α ≤ ω2 + 1, an elementary amenable group of elementary class α (under Chou's stratification of elementary amenable groups) that is a subgroup of F and thus of PLo(I). We also give examples that negatively answer a question of Sapir about non-solvable groups in F and PLo(I).

scholarly journals On elementary amenable groups of finite Hirsch number

1995 ◽  
Vol 58 (2) ◽  
pp. 219-221 ◽  
Author(s):  
B. A. F. Wehrfritz
Keyword(s):  
Normal Subgroup ◽  
Short Proof ◽  
Amenable Group ◽  
Locally Finite ◽  
Amenable Groups ◽  
Derived Length ◽  
Recent Theorem

AbstractWe give an alternative short proof of a recent theorem of J. A. Hillman and P.A. Linnell that an elementary amenable group with finite Hirsch number has, modulo its locally finite radical, a soluble normal subgroup with index and derived length bounded only in terms of the Hirsch number of the group.

On a construction of unitary cocycles and the representation theory of amenable groups

1983 ◽  
Vol 3 (1) ◽  
pp. 129-133 ◽  
Author(s):  
Colin E. Sutherland
Keyword(s):  
Representation Theory ◽  
Probability Space ◽  
Amenable Group ◽  
Unitary Representations ◽  
Intertwining Operators ◽  
Type I ◽  
Amenable Groups

AbstractIf K is a countable amenable group acting freely and ergodically on a probability space (Γ, μ), and G is an arbitrary countable amenable group, we construct an injection of the space of unitary representations of G into the space of unitary 1-cocyles for K on (Γ, μ); this injection preserves intertwining operators. We apply this to show that for many of the standard non-type-I amenable groups H, the representation theory of H contains that of every countable amenable group.

A Note on Brauer Character Degrees of Solvable Groups

1991 ◽  
Vol 34 (3) ◽  
pp. 423-425 ◽  
Author(s):  
You-Qiang Wang
Keyword(s):  
Solvable Group ◽  
Solvable Groups ◽  
Character Degrees ◽  
Finite Solvable Group ◽  
Prime Integer ◽  
Derived Length ◽  
Brauer Character ◽  
Brauer Characters

AbstractLet G be a finite solvable group. Fix a prime integer p and let t be the number of distinct degrees of irreducible Brauer characters of G with respect to the prime p. We obtain the bound 3t — 2 for the derived length of a Hall p'-subgroup of G. Furthermore, if |G| is odd, then the derived length of a Hall p'-subgroup of G is bounded by /.

Weak Convergence Is Not Strong Convergence For Amenable Groups

2001 ◽  
Vol 44 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Joseph M. Rosenblatt ◽  
George A. Willis
Keyword(s):  
Weak Convergence ◽  
Strong Convergence ◽  
Cayley Graphs ◽  
Linear Equations ◽  
Amenable Group ◽  
Amenable Groups

AbstractLet G be an infinite discrete amenable group or a non-discrete amenable group. It is shown how to construct a net (fα) of positive, normalized functions in L1(G) such that the net converges weak* to invariance but does not converge strongly to invariance. The solution of certain linear equations determined by colorings of the Cayley graphs of the group are central to this construction.

Non-Bernoulli systems with completely positive entropy

2008 ◽  
Vol 28 (1) ◽  
pp. 87-124 ◽  
Author(s):  
A. H. DOOLEY ◽  
V. YA. GOLODETS ◽  
D. J. RUDOLPH ◽  
S. D. SINEL’SHCHIKOV
Keyword(s):  
Infinite Order ◽  
Amenable Group ◽  
Positive Entropy ◽  
Completely Positive ◽  
New Approach ◽  
Amenable Groups ◽  
Uncountable Family ◽  
Cutting And Stacking ◽  
Bernoulli Systems

AbstractA new approach to actions of countable amenable groups with completely positive entropy (cpe), allowing one to answer some basic questions in this field, was recently developed. The question of the existence of cpe actions which are not Bernoulli was raised. In this paper, we prove that every countable amenable groupG, which contains an element of infinite order, has non-Bernoulli cpe actions. In fact we can produce, for any$h \in (0, \infty ]$, an uncountable family of cpe actions of entropyh, which are pairwise automorphically non-isomorphic. These actions are given by a construction which we call co-induction. This construction is related to, but different from the standard induced action. We study the entropic properties of co-induction, proving that ifαGis co-induced from an actionαΓof a subgroup Γ, thenh(αG)=h(αΓ). We also prove that ifαΓis a non-Bernoulli cpe action of Γ, thenαGis also non-Bernoulli and cpe. Hence the problem of finding an uncountable family of pairwise non-isomorphic cpe actions of the same entropy is reduced to one of finding an uncountable family of non-Bernoulli cpe actions of$\mathbb Z$, which pairwise satisfy a property we call ‘uniform somewhat disjointness’. We construct such a family using refinements of the classical cutting and stacking methods.

Solvable groups with restrictions on Sylow subgroups of the Fitting subgroup

2016 ◽  
Vol 09 (02) ◽  
pp. 1650037
Author(s):  
Alexander Trofimuk
Keyword(s):  
Free Groups ◽  
Solvable Groups ◽  
Fitting Subgroup ◽  
Sylow Subgroups ◽  
Nilpotent Length ◽  
Derived Length ◽  
Odd Order

In this paper, we study solvable groups in which [Formula: see text] is at most 2. In particular, we investigated groups of odd order and [Formula: see text]-free groups with this property. Exact estimations of the derived length and nilpotent length of such groups are obtained.

scholarly journals A presentation for a group of automorphisms of a simplicial complex

1988 ◽  
Vol 30 (3) ◽  
pp. 331-337 ◽  
Author(s):  
M. A. Armstrong
Keyword(s):  
Simplicial Complex ◽  
Elementary Proof ◽  
Universal Covering ◽  
Covering Space ◽  
Covering Spaces ◽  
Group Of Automorphisms ◽  
Generators And Relations ◽  
Universal Covering Space ◽  
Simply Connected ◽  
Special Case

The Bass–Serre theorem supplies generators and relations for a group of automorphisms of a tree. Recently K. S. Brown [2] has extended the result to produce a presentation for a group of automorphisms of a simply connected complex, the extra ingredient being relations which come from the 2-cells of the complex. Suppose G is the group, K the complex and L the 1-skeleton of K. Then an extension of π1(L) by G acts on the universal covering space of L (which is of course a tree) and Brown's technique is to apply the work of Bass and Serre to this action. Our aim is to give a direct elementary proof of Brown's theorem which makes no use of covering spaces, deals with the Bass–Serre theorem as a special case and clarifies the roles played by the various generators and relations.

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