scholarly journals The radical of the group algebra of a sub-group, of a polycyclic group and of a restricted SN-group

1970 ◽  
Vol 17 (2) ◽  
pp. 165-171 ◽  
Author(s):  
D. A. R. Wallace
Keyword(s):  
Group Algebra ◽  
Jacobson Radical ◽  
Zero Element ◽  
Closed Field ◽  
Nilpotent Ideal ◽  
Locally Finite ◽  
Locally Nilpotent ◽  
Image Position ◽  
Necessary And Sufficient ◽  
The Relationship

Let G be a group and let K be an algebraically closed field of characteristic p>0. The twisted group algebra Kt(G) of G over K is defined as follows: let G have elements a, b, c, … and let Kt(G) be a vector space over K with basis elements , …; a multiplication is defined on this basis of Kt(G) and extended by linearity to Kt(G) by lettingwhere α(x, y) is a non-zero element of K, subject to the condition thatwhich is both necessary and sufficient for associativity. If, for all x, y ∈ G, α{x, y) is the identity of K then Kt(G) is the usual group algebra K(G) of G over K. We denote the Jacobson radical of Kt(G) by JKt(G). We are interested in the relationship between JKt(G) and JKt(H) where H is a normal subgroup of G. In § 2 we show, among other results, that if certain centralising conditions are satisfied and if JK(H) is locally nilpotent then JK(H)K(G) is also locally nilpotent and thus contained in JK(G). It is observed that in the absence of some centralising conditions these conclusions are false. We show, in particular, that if H and G/C(H) are locally finite, C(H) being the centraliser of H, and if G/H has no non-trivial elements of order p, then JK(G) coincides with the locally nilpotent ideal JK(H)K(G). The latter, and probably more significant, part of this paper is concerned with particular types of groups. We introduce the notion of a restricted SN-group and show that if G is such a group and if G has no non-trivial elements of order p then JKt(G) = {0}. It is also shown that if G is polycyclic then JKt(G) is nilpotent.

On Group Rings

1970 ◽  
Vol 22 (2) ◽  
pp. 249-254 ◽  
Author(s):  
D. B. Coleman
Keyword(s):  
Nilpotent Group ◽  
Commutative Ring ◽  
Group Ring ◽  
Characteristic Zero ◽  
Sylow Subgroup ◽  
Jacobson Radical ◽  
Closed Field ◽  
Group Rings ◽  
Locally Finite ◽  
Image Position

Let R be a commutative ring with unity and let G be a group. The group ring RG is a free R-module having the elements of G as a basis, with multiplication induced byThe first theorem in this paper deals with idempotents in RG and improves a result of Connell. In the second section we consider the Jacobson radical of RG, and we prove a theorem about a class of algebras that includes RG when G is locally finite and R is an algebraically closed field of characteristic zero. The last theorem shows that if R is a field and G is a finite nilpotent group, then RG determines RP for every Sylow subgroup P of G, regardless of the characteristic of R.

scholarly journals Closure operations and group algebras

1972 ◽  
Vol 18 (2) ◽  
pp. 149-158 ◽  
Author(s):  
J. D. P. Meldrum ◽  
D. A. R. Wallace
Keyword(s):  
Vector Space ◽  
Associative Algebra ◽  
Group Algebra ◽  
Jacobson Radical ◽  
Group Algebras ◽  
Twisted Group Algebra ◽  
Twisted Group ◽  
Closure Operations ◽  
Image Position

Let G be a group and let K be a field. The twisted group algebra Kt(G) of G over K is defined as follows: let G have elements a, b, c, … and let Kt(G) be the vector space over K with basis elements ; let α: G ×G → K be a 2-cocycle and define a multiplication on Kt(G) byextending this by linearity to Kt(G) yields an associative algebra. We are interested in information concerning the Jacobson radical of Kt(G), denoted by JKt(G).

Basis normalizers and Carter subgroups in a class of locally finite groups

1972 ◽  
Vol 71 (2) ◽  
pp. 189-198 ◽  
Author(s):  
C. J. Graddon ◽  
B. Hartley
Keyword(s):  
Finite Groups ◽  
Locally Finite ◽  
Locally Finite Groups ◽  
Finite Series ◽  
Locally Nilpotent ◽  
Image Position

We shall be working throughout this paper in the class of locally finite groups introduced in (3) and further discussed in (5) and (6), and all groups appearing will be assumed to belong to this class. By definition, is the largest subgroupclosed class of locally finite groups satisfying the conditions:U1. If G ε then G has a finite serieswith locally nilpotent factors.

MAXIMAL SUBGROUPS OF SOME NON LOCALLY FINITE p-GROUPS

2005 ◽  
Vol 15 (05n06) ◽  
pp. 1129-1150 ◽  
Author(s):  
E. L. PERVOVA
Keyword(s):  
Maximal Subgroup ◽  
Group Algebra ◽  
Infinite Series ◽  
Jacobson Radical ◽  
Maximal Subgroups ◽  
Augmentation Ideal ◽  
Finitely Generated ◽  
Characteristic P ◽  
Locally Finite ◽  
Ideal Formula

Kaplansky's conjecture claims that the Jacobson radical [Formula: see text] of a group algebra K[G], where K is a field of characteristic p > 0, coincides with its augmentation ideal [Formula: see text] if and only if G is a locally finite p-group. By a theorem of Passman, if G is finitely generated and [Formula: see text] then any maximal subgroup of G is normal of index p. In the present paper, we consider one infinite series of finitely generated infinite p-groups (hence not locally finite p-groups), so called GGS-groups. We prove that their maximal subgroups are nonetheless normal of index p. Thus these groups remain among potential counterexamples to Kaplansky's conjecture.

Random walk and electric currents in networks

1959 ◽  
Vol 55 (2) ◽  
pp. 181-194 ◽  
Author(s):  
C. St J. A. Nash-Williams
Keyword(s):  
Random Walk ◽  
Electrical Network ◽  
Positive Real ◽  
Geometrical Characterization ◽  
Locally Finite ◽  
Biased Random Walk ◽  
Geometrical Character ◽  
Complementary Set ◽  
Image Position ◽  
Necessary And Sufficient

ABSTRACTLet G be a locally finite connected graph and c be a positive real-valued function defined on its edges. Let D(ξ) denote the sum of the values of c on the edges incident with a vertex ξ. A particle starts at some vertex α and performs an infinite random walkin which (i) the ξj are vertices of G, (ii), λj. is an edge joining ξj–1 to ξj (j = 1, 2, 3, …), (iii) if λ is any edge incident with ξj, thenLet υ be a set of vertices of G such that the complementary set of vertices is finite and includes α. A geometrical characterization is given of the probability (τ, say) that the particle will visit some element of υ without first returning to α. An essentially equivalent problem is obtained by regarding G as an electrical network and c(λ) as the conductance of an edge λ; the current flowing through the network from α to υ when an external agency maintains α at potential I and all elements of υ at potential 0 is found to be τD(α).A necessary and sufficient condition (of a geometrical character) for the particle to be certain to return to α. is obtained; and, as an application, a new proof is given of a conjecture of Gillis (3) regarding centrally biased random walk on an n–dimensional lattice.

20.—Deficiency Indices of Polynomials in Symmetric Differential Expressions, II

1975 ◽  
Vol 73 ◽  
pp. 301-306 ◽  
Author(s):  
Anton Zettl
Keyword(s):  
Hilbert Space ◽  
Differential Expression ◽  
Sufficient Condition ◽  
Necessary And Sufficient Condition ◽  
Real Polynomial ◽  
Deficiency Indices ◽  
Linear Differential ◽  
Image Position ◽  
Necessary And Sufficient ◽  
The Relationship

SynopsisGiven a symmetric (formally self-adjoint) ordinary linear differential expression L which is regular on the interval [0, ∞) and has C∞ coefficients, we investigate the relationship between the deficiency indices of L and those of p(L), where p(x) is any real polynomial of degree k > 1. Previously we established the following inequalities: (a) For k even, say k = 2r, N+(p(L)), N−(p(L)) ≧ r[N+(L)+N−(L)] and (b) for k odd, say k = 2r+1where N+(M), N−(M) denote the deficiency indices of the symmetric expression M (or of the minimal operator associated with M in the Hilbert space L2(0, ∞)) corresponding to the upper and lower half-planes, respectively. Here we give a necessary and sufficient condition for equality to hold in the above inequalities.

Complete Reductibility of Infinite Groups

1964 ◽  
Vol 16 ◽  
pp. 267-274 ◽  
Author(s):  
John D. Dixon
Keyword(s):  
Nilpotent Group ◽  
Similarity Transformation ◽  
Matrix Representation ◽  
Closed Field ◽  
Extension Field ◽  
Perfect Field ◽  
Infinite Groups ◽  
Locally Nilpotent ◽  
Completely Reducible ◽  
Necessary And Sufficient

The theorems of the present paper deal with conditions which are necessary and sufficient in order that a solvable or nilpotent infinite group should have a completely reducible matrix representation over a given algebraically closed field.It is known (17) that a locally nilpotent group of matrices is always solvable. Thus the first theorem of the present paper is a partial generalization of Theorem 1 of (16), which states:If G is a locally nilpotent subgroup of the full linear group GL(n, P) over a perfect field P, then G is completely reducible if and only if each matrix of G is diagonizable (by a similarity transformation over some extension field of P).

Invariants of finite-dimensional algebras recognized by the semigroup of conjugacy classes of left ideals

2017 ◽  
Vol 16 (10) ◽  
pp. 1750182
Author(s):  
Arkadiusz Mȩcel ◽  
Jan Okniński
Keyword(s):  
Jacobson Radical ◽  
Semigroup Algebra ◽  
Conjugacy Classes ◽  
Maximal Subgroups ◽  
Closed Field ◽  
Finite Dimensional Algebra ◽  
Dimensional Algebra ◽  
Locally Finite ◽  
Finite Dimensional ◽  
Ordinary Quiver

We study the semigroup structure on the set [Formula: see text] of conjugacy classes of left ideals of a finite-dimensional algebra [Formula: see text] over an algebraically closed field [Formula: see text], equipped with the natural multiplication inherited from [Formula: see text], and the structure of the contracted semigroup algebra [Formula: see text]. It is shown that [Formula: see text] has a finite chain of ideals with either nilpotent or completely [Formula: see text]-simple factors with trivial maximal subgroups, so in particular it is locally finite. The ordinary quiver [Formula: see text] of [Formula: see text] is proved to be a subquiver of [Formula: see text], if [Formula: see text] is finite. Moreover, in this case, the structure of [Formula: see text] determines, up to isomorphism, the structure of the algebra [Formula: see text] modulo its Jacobson radical. Combining these results we show that if the semigroup [Formula: see text] is finite, then it determines the structure of any (not necessarily basic) triangular algebra [Formula: see text] which admits a normed presentation.

scholarly journals Lower bounds for the radical of the group algebra of a finite p-soluble group

1968 ◽  
Vol 16 (2) ◽  
pp. 127-134 ◽  
Author(s):  
D. A. R. Wallace
Keyword(s):  
Finite Group ◽  
Lower Bound ◽  
Lower Bounds ◽  
Group Algebra ◽  
Jacobson Radical ◽  
Soluble Group ◽  
Nilpotent Ideal ◽  
A Finite Group ◽  
Radical Form

Over a field of characteristic p>0 the group algebra of a finite group has a unique maximal nilpotent ideal, the Jacobson radical of the algebra. The powers of the radical form a decreasing and ultimately vanishing series of ideals and it would be of interest to determine the least vanishing power. Apart from the work of Jennings (3) on p-groups little is known in general (cf. (5)) about this particular power of the radical (cf. Remarks of Brauer in (4), p. 144. Problem 15). In this paper we give non-trivial lower bounds for the index of the least vanishing power of the radical when the group is p-soluble. Of the lower bounds we give we show that that lower bound, which is dependent solely on the order of the group, is the best possible such bound and that this bound is invalid if the assumption of p-solubility is omitted.

GROUP ALGEBRAS WITH ENGEL UNIT GROUPS

2016 ◽  
Vol 101 (2) ◽  
pp. 244-252 ◽  
Author(s):  
M. RAMEZAN-NASSAB
Keyword(s):  
Normal Subgroup ◽  
Group Algebra ◽  
Group Algebras ◽  
Abelian Normal Subgroup ◽  
Locally Finite ◽  
Engel Group ◽  
Group Of Units ◽  
Nilpotent Elements ◽  
Locally Nilpotent ◽  
Formula Group

Let $F$ be a field of characteristic $p\geq 0$ and $G$ any group. In this article, the Engel property of the group of units of the group algebra $FG$ is investigated. We show that if $G$ is locally finite, then ${\mathcal{U}}(FG)$ is an Engel group if and only if $G$ is locally nilpotent and $G^{\prime }$ is a $p$-group. Suppose that the set of nilpotent elements of $FG$ is finite. It is also shown that if $G$ is torsion, then ${\mathcal{U}}(FG)$ is an Engel group if and only if $G^{\prime }$ is a finite $p$-group and $FG$ is Lie Engel, if and only if ${\mathcal{U}}(FG)$ is locally nilpotent. If $G$ is nontorsion but $FG$ is semiprime, we show that the Engel property of ${\mathcal{U}}(FG)$ implies that the set of torsion elements of $G$ forms an abelian normal subgroup of $G$.

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