N-Series and Filtrations of the Augmentation Ideal

1974 ◽  
Vol 26 (4) ◽  
pp. 962-977 ◽  
Author(s):  
Gerald Losey
Keyword(s):  
Abelian Group ◽  
Group Ring ◽  
Free Abelian Group ◽  
Augmentation Ideal ◽  
Free Basis ◽  
Image Position

Let G be a group. Denote by ZG the group ring of G over the integers and by Δ = Δ(G) the augmentation ideal of ZG, that is, the kernel of the augmentation map ϵ : ZG → Z defined by . Then Δ is a free abelian group with a free basis . A filtration of Δ is a sequence

The associated graded ring of an integral group ring

1977 ◽  
Vol 82 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Inder Bir S. Passi ◽  
Lekh Raj Vermani
Keyword(s):  
Abelian Group ◽  
Group Ring ◽  
Symmetric Algebra ◽  
Integral Group Ring ◽  
Augmentation Ideal ◽  
Integral Group ◽  
Finite Abelian Groups ◽  
Associated Graded Ring ◽  
Graded Ring ◽  
Image Position

Let G be an Abelian group, the symmetric algebra of G and the associated graded ring of the integral group ring ZG, where (AG denotes the augmentation ideal of ZG). Then there is a natural epimorphism (4)which is given on the nth component byIn general θ is not an isomorphism. In fact Bachmann and Grünenfelder(1) have shown that for finite Abelian G, θ is an isomorphism if and only if G is cyclic. Thus it is of interest to investigate ker θn for finite Abelian groups. In view of proposition 3.25 of (3) it is enough to consider finite Abelian p-groups.

scholarly journals On the group ring of a finite abelian group

1969 ◽  
Vol 1 (2) ◽  
pp. 245-261 ◽  
Author(s):  
Raymond G. Ayoub ◽  
Christine Ayoub
Keyword(s):  
Finite Group ◽  
Abelian Group ◽  
Group Ring ◽  
Free Abelian Group ◽  
Finite Abelian Group ◽  
Rational Numbers ◽  
Cyclotomic Fields ◽  
Group Of Units ◽  
Direct Sum ◽  
A Finite Group

The group ring of a finite abelian group G over the field of rational numbers Q and over the rational integers Z is studied. A new proof of the fact that the group ring QG is a direct sum of cyclotomic fields is given – without use of the Maschke and Wedderburn theorems; it is shown that the projections of QG onto these fields are determined by the inequivalent characters of G. It is proved that the group of units of ZG is a direct product of a finite group and a free abelian group F and the rank of F is determined. A formula for the orthogonal idempotents of QG is found.

Augmentation quotients of group rings and symmetric powers

1979 ◽  
Vol 85 (2) ◽  
pp. 247-252 ◽  
Author(s):  
Robert Sandling ◽  
Ken-Ichi Tahara
Keyword(s):  
Finite Group ◽  
Abelian Group ◽  
Additive Group ◽  
Lower Central Series ◽  
Symmetric Power ◽  
Central Series ◽  
Group Rings ◽  
Augmentation Ideal ◽  
Symmetric Powers ◽  
Image Position

Let G be a group with the lower central seriesLetwhere Σ runs over all non-negative integers a1, a2,…, an such that and is the aith symmetric power of the abelian group Gi/Gi+1 whereLet I (G) be the augmentation ideal of G in , the group ring of G over . Define the additive group Qn (G) = In (G) / In+1 (G) for any n ≥ 1. Then it is well known that Q1(G) ≅ W1(G) for any group G. Losey (4,5) proved that Q2(G) ≅ W2(G) for any finitely generated group G. Furthermore recently Tahara(12) proved that Q3(G) is a certain precisely defined quotient of W3(G) for any finite group G.

On the Structure of Q2(G) for Finitely Generated Groups

1973 ◽  
Vol 25 (2) ◽  
pp. 353-359 ◽  
Author(s):  
Gerald Losey
Keyword(s):  
Abelian Group ◽  
Group Ring ◽  
Lower Central Series ◽  
Integral Group Ring ◽  
Symmetric Power ◽  
Central Series ◽  
Augmentation Ideal ◽  
Integral Group ◽  
Finitely Generated ◽  
Finitely Generated Groups

Let G be a group, ZG its integral group ring and Δ = Δ(G) the augmentation ideal of ZG. Denote by Gi the ith term of the lower central series of G. Following Passi [3], we set . It is well-known that (see, for example [1]). In [3] Passi shows that if G is an abelian group then , the second symmetric power of G.

scholarly journals On the automorphisms of the group ring of a finitely generated free abelian group

1988 ◽  
Vol 31 (1) ◽  
pp. 71-75
Author(s):  
M. M. Parmenter
Keyword(s):  
Abelian Group ◽  
Prime Ideal ◽  
Group Ring ◽  
Associative Ring ◽  
Free Abelian Group ◽  
Finitely Generated ◽  
Torsion Free Abelian Group ◽  
Special Case ◽  
Torsion Free

Let R be an associative ring with 1 and G a finitely generated torsion-free abelian group. In this note, we classify all R-automorphisms of the group ring RG. The special case where G is infinite cyclic was previously settled in [8], and our interest in this problem was rekindled by the recent paper of Mehrvarz and Wallace [7], who carried out the classification in the case where R contains a nilpotent prime ideal.

Cyclic Cohomology of Non-Commutative Tori

1988 ◽  
Vol 40 (5) ◽  
pp. 1046-1057 ◽  
Author(s):  
Ryszard Nest
Keyword(s):  
Abelian Group ◽  
Exact Sequence ◽  
Finite Rank ◽  
Hochschild Cohomology ◽  
Free Abelian Group ◽  
Cyclic Cohomology ◽  
Irrational Rotation ◽  
Rational Case ◽  
Image Position

In this paper we shall compute the cyclic cohomology of a non-commutative torus, i.e., a certain algebra associated with an antisymmetric bicharacter of a finite rank free abelian group G.The main result is1.1whereThe method of computation generalises the computation of the cyclic cohomology of the irrational rotation algebras given by Connes in [3]. (Our method works equally well also in the rational case, which was dealt with by a different method by Connes in [3].)We first describe the Hochschild cohomology of in an explicit way, and then combine this description with the exact sequence of [3]:1.2

On polynomial groups

1970 ◽  
Vol 68 (2) ◽  
pp. 285-289 ◽  
Author(s):  
L. R. Vermani
Keyword(s):  
Group Ring ◽  
Abelian Groups ◽  
Integral Group Ring ◽  
Augmentation Ideal ◽  
Integral Group ◽  
Image Position

If M is a group, Z(M) its integral group ring and AM the augmentation ideal, then following Passi we can form the Abelian groups

The projective extensions of a finite group

1981 ◽  
Vol 90 (2) ◽  
pp. 251-257
Author(s):  
P. J. Webb
Keyword(s):  
Finite Group ◽  
Group Ring ◽  
Projective Module ◽  
Integral Group Ring ◽  
Augmentation Ideal ◽  
Integral Group ◽  
Definition Of ◽  
Image Position ◽  
A Finite Group ◽  
Exact Sequences

Let G be a finite group and let g be the augmentation ideal of the integral group ring G. Following Gruenberg(5) we let (g̱) denote the category whose objects are short exact sequences of zG-modules of the form and in which the morphisms are commutative diagramsIn this paper we describe the projective objects in this category. These are the objects which satisfy the usual categorical definition of projectivity, but they may also be characterized as the short exact sequencesin which P is a projective module.

Sums of Complexes in Torsion Free Abelian Groups

1969 ◽  
Vol 12 (4) ◽  
pp. 479-480 ◽  
Author(s):  
H. Heilbronn ◽  
P. Scherk
Keyword(s):  
Abelian Group ◽  
Free Abelian Group ◽  
Abelian Groups ◽  
Preceding Paper ◽  
Torsion Free Abelian Group ◽  
Linearly Independent ◽  
Free Abelian Groups ◽  
Image Position ◽  
Torsion Free

Let A, B, denote two non-void finite complexes (= subsets) of the torsion free abelian group G,Let d(A),… denote the maximum number of linearly independent elements of A,… and let n = n(A, B) denote the number of elements of A + B whose representation in the form a + b is unique. In the preceding paper, Tarwater and Entringer [1] proved that n ≥ d(A).

Polynomial functors

1969 ◽  
Vol 66 (3) ◽  
pp. 505-512 ◽  
Author(s):  
I. B. S. Passi
Keyword(s):  
Group Ring ◽  
Abelian Groups ◽  
Integral Group Ring ◽  
Recent Theory ◽  
Augmentation Ideal ◽  
Integral Group ◽  
Polynomial Functors ◽  
Derived Functors ◽  
Image Position

1. Introduction: If G is a group, Z(G) its integral group-ring and AG the augmentation ideal, then we can form the Abelian groupsIn (5) we have studied the structure of these Abelian groups which we called polynomial grouups. If C denotes the category of Abelian groups, then Pn and Qn are functors from C into C. We call these functors polynomial functors. The object of this work is to study the nature of these funtors. Except for n = 1, these functors are non-additive. In fact, in the sense of Eilenberg–Maclane (4) these are functors of degree exactly n (Theorem 2·3). Because of their non-additive nature, their derived functors cannot be calculated in the traditional Cartan–Eilenberg(1) method. We have to make use of the more recent theory of Dold–Puppe (3).

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