Groups with virtually abelian proper quotients

Radicals in Abelian Groups

1·1. We shall write for the class of groups all of whose non-trivial normal subgroups have finite index. Thus, rather obviously, finite groups, simple groups, and the infinite cyclic and dihedral groups all lie in the class . Other examples of -groups are to be found in a variety of contexts. The main result of Mennicke (8) shows that, for n ≥ 3, the factor group of SL(n, Z) by its centre is a -group, where SL(n, Z) denotes the unimodular group of all n × n invertible matrices with integer coefficients and with determinant 1. In McLain(7), an example is given of an infinite, locally finite, locally soluble -group, whose only non-trivial normal subgroups are the terms of its derived series, and in (4), P. Hall discusses an infinite -group, all of whose proper quotients are finite p-groups. If is a class of groups closed under taking homomorphic images, it is easily seen that the existence of an infinite -group satisfying the maximal condition for normal subgroups implies the existence of an infinite -group in the class , so that certain questions concerning the finiteness of groups satisfying the maximal condition for normal subgroups can be interpreted as questions about -groups.

Characterization of almost maximally almost-periodic groups

In this paper, we shall discuss some recent contributions to the project [15, 14, 2, 18, 22, 23] of explaining why no satisfactory system of complete invariants has yet been found for the torsion-free abelian groups of finite rank n ≥ 2. Recall that, up to isomorphism, the torsion-free abelian groups of rank n are exactly the additive subgroups of the n-dimensional vector space ℚn which contain n linearly independent elements. Thus the collection of torsion-free abelian groups of rank at most n can be naturally identified with the set S (ℚn) of all nontrivial additive subgroups of ℚn. In 1937, Baer [4] solved the classification problem for the class S(ℚ)of rank 1 groups as follows.Let ℙ be the set of primes. If G is a torsion-free abelian group and 0 ≠ x ϵ G, then the p-height of x is defined to behx(p) = sup{n ϵ ℕ ∣ There exists y ϵ G such that pny = x} ϵ ℕ ∪{∞}; and the characteristic χ (x) of x is defined to be the function

Fast Fourier analysis for abelian group extensions

Let G be a locally compact abelian group with a Haar measure lambda(G). A function f on G is said to be mean-periodic if there exists a nonzero finite regular measure mu of compact support on G such that f*mu = 0. It is known that there exist no nontrivial integrable mean periodic functions on R(n) . We show that there exist nontrivial integrable mean periodic functions on G provided G has nontrivial proper compact subgroups. Let f is-an-element-of L1 (G) be mean periodic with respect to a nonzero finite measure mu of compact support. If mu(G) not-equal 0 and lambda(G) (SUPP(mu)) > 0 , then there exists a compact subgroup K of G such that f*lambda(K) = 0, i.e., f is mean periodic with respect to lambda(K) , where lambda(K) denotes the normalized Haar measure of K. When G is compact, abelian and meterizable, we show that there exists continuous (hence integrable and almost periodic) functions on G that arc not mean periodic.

We extend the definition of a finite -group to profinite groups and give a description of profinite -groups as a triple semidirect product of two prosoluble groups with a semisimple group, extending an old result of A. M. Broshi to the profinite case. We also prove that a profinite -group with finitely generated non-trivial Fitting subgroup is metabelian-by-(finite exponent). If, in addition, G is finitely generated then it is virtually metabelian polycyclic. Communicated by Mandi Schaeffer Fry

Methods and results from the representation theory of finite di- mensional algebras have led to many interactions with other areas of mathe- matics. Such areas include the theory of Lie algebras and quantum groups, commutative algebra, algebraic geometry and topology, and in particular the new theory of cluster algebras. The aim of this workshop was to further de- velop such interactions and to stimulate progress in the representation theory of algebras.

In this brief chapter we present a quantum algorithm, which can be seen as a generalization of Shor’s algorithm. We can here explain, in a more structural manner, why quantum computers can speed up some computational problems. The so-called Simon’s hidden subgroup problem can be stated in a general form as follows [18]: Input: A finite abelian group G and function ρ: G → R, where R is a finite set. Promise: There exists a nontrivial subgroup H ≤ G such that ρ is constant and distinct on each coset of H. Output: A generating set for H.