On Primitive Representations of Minimax Nilpotent Groups

We show, in particular, that in the class of minimax two-step nilpotent groups only finitely generated groups can admit exact irreducible primitive representations over a finitely generated field of characteristic zero. We also suggest some approaches to studying induced representations of nilpotent groups of finite rank.     

The Two-Step Nilpotent Representations of the Extended Affine Hecke Algebra of Type A

We define a set of cell modules for the extended affine Hecke algebra of type A which are parametrised by SL_n()-conjugacy classes of pairs (s, N), where s SL_n() is semisimple and N is a nilpotent element of the Lie algebra which has at most two Jordan blocks and satisfies Ad(s)·N=q ² N. When q ²–1, each of these has irreducible head, and the irreducible representations of the affine Hecke algebra so obtained are precisely those which factor through its Temperley–Lieb quotient. When q ²=–1, the above remarks apply to a subset of the cell modules. Using our work on the cellular nature of those quotients, we are able to obtain complete information on the decomposition of the cell modules in all cases, even when q is a root of unity. They turn out to be multiplicity free, and the composition factors may be precisely described in terms of a partial order on the pairs (s, N). These results give explicit formulae for the dimensions of the irreducibles. Assuming our modules are identified with the standard modules earlier defined by Bernstein–Zelevinski, Kazhdan–Lusztig and others, our results may be interpreted as the determination of certain Kazhdan–Lusztig polynomials. [This has now been proved and will appear in a subsequent work of the authors.]The second author thanks the Australian Research Council and the Alexander von Humboldt Stiftung for support and the Universität Bielefeld for hospitality during the preparation of this work.     

Invertible and Nilpotent Elements in the Group Algebra of a Unique Product Group

We describe the nilpotent and invertible elements in group algebras k[G] for k a commutative associative unital ring and G a unique product group, for example an ordered group.     

Finite Factor Representations of 2-Step Nilpotent Groups and the Orbit Method

In this paper, we describe factor representations of discrete 2-step nilpotent groups with 2-divisible center in the spirit of the orbit method. We show that some standard theorems of the orbit method are valid for these groups. In the case of countable 2-step nilpotent groups we explain how to construct a factor representation starting with an orbit of the “coadjoint representation.” We also prove that every factor representation (more precisely, every trace) can be obtained by this construction, and prove a theorem on the decomposition of a factor representation restricted to a subgroup. Bibliography: 7 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 307, 2004, pp. 120–140.     

Clifford Theory for Glider Representations

Classical Clifford theory studies the decomposition of simple G-modules into simple H-modules for some normal subgroup H ? G. In this paper we deal with chains of normal subgroups 1?G ₁?· · ·?G _d = G, which allow to consider fragments and in particular glider representations. These are given by a descending chain of vector spaces over some field K and relate different representations of the groups appearing in the chain. Picking some normal subgroup H ? G one obtains a normal subchain and one can construct an induced fragment structure. Moreover, a notion of irreducibility of fragments is introduced, which completes the list of ingredients to perform a Clifford theory.     

On the Howson Property of HNN-Extensions with Nilpotent Base Group and Amalgamated Free Products of Nilpotent Groups

We give necessary and sufficient conditions under which an amalgamated free product of finitely generated nilpotent groups is a Howson group (that is the intersection of any two finitely generated subgroups is finitely generated). Also we prove that if G = ? t, K | t ^?1 At = B ?, where K is a finitely generated and infinite nilpotent group and A, B non-trivial infinite proper subgroups of K, then G is not a Howson group. The problem of deciding when an ascending HNN-extension of a finitely generated nilpotent group is a Howson group is still open.     

有限幂零群通过单群扩张的整群环的正规化子性质

设G是一个有限幂零群通过单群的扩张,即G有一个幂零正规子群N,使得G/N是单群.本文证明了这样的有限群G具有正规化子性质.特别地,内可解群有正规化子性质.     

有限幂零群通过对称群扩张的整群环的正规化子性质

设G是一个有限幂零群Ⅳ通过m次对称群S_m的扩张,本文证明了G有正规化子性质.我们的定理推广了Petit Lobao与Sehgal的一个结果:设G=N(?) S_m是一个有限幂零群N与对称群S_m的自然圈积,则G有正规化子性质.我们的方法不同于Petit Lobao与Sehgal的方法.     

On Co-Hopfian Nilpotent Groups

Co-Hopfian finitely generated torsion-free nilpotent groupsare characterized in this paper in terms of their Lie algebraautomorphisms. Many examples of such groups are also constructed.2000 Mathematics Subject Classification 17B30, 20F18 (primary).     

Properties of a Finite Group Representable as the Product of Two Nilpotent Groups

We establish a series of new properties of a finite group G = AB with nilpotent subgroups A and B.     

Non-Commuting Graphs of Nilpotent Groups

Let G be a non-abelian group and Z(G) be the center of G. The non-commuting graph Γ _G associated to G is the graph whose vertex set is G?Z(G) and two distinct elements x, y are adjacent if and only if xy ≠ yx. We prove that if G and H are non-abelian nilpotent groups with irregular isomorphic non-commuting graphs, then |G| = |H|.     

Quasivarieties with Torsion-Free Nilpotent Groups

A condition is specified on which a quasivariety generated by a direct product of two groups with amalgamated central subgroups has an infinite lattice of subquasivarieties. A lattice of quasivarieties is stated finite for a quasivariety which is a union of some covers of Abelian groups in a lattice of quasivarieties of torsion-free solvable groups.     

Groups that are Pairwise Nilpotent

In this article we study groups generated by a set X with the property that every two elements in X generate a nilpotent subgroup.     

一类Witt代数的包络代数的表示

设C为复数域,P,q∈C,且pq是m次本原单位根．我们构造了一个Zm-分次模类V(a,b),它为Witt代数的包络代数的(P,q)变形U(Wpq)的Zm-分次模类,并证明了任何一个Zm-分次U(Wpq)-模都与某个V(a,b)同构．     

Hypercentral Unit Groups and the Hyperbolicity of a Modular Group Algebra

We classify groups G such that the unit group 𝒰 ₁(? G) is hypercentral. In the second part, we classify groups G whose modular group algebra has hyperbolic unit groups 𝒰 ₁(KG).     

$$L^p$$ L p -Multipliers Sensitive to the Group Structure on Nilpotent Lie Groups

Journal of Fourier Analysis and Applications - We propose new sufficient conditions for $$L^p$$ -multipliers on homogeneous nilpotent groups. The multipliers generalise the flag multipliers of...     

The Automorphism Group of a Class of Nilpotent Groups with Infinite Cyclic Derived Subgroups

The automorphism group of a class of nilpotent groups with infinite cyclic derived subgroups is determined. Let G be the direct product of a generalized extraspecial Z-group E and a free abelian group A with rank m, where E ={(1 kα_1 kα_2 ··· kα_nα_(n+1) 0 1 0 ··· 0 α_(n+2)...............000...1 α_(2n+1)000...01|αi∈ Z, i = 1, 2,..., 2 n + 1},where k is a positive integer. Let AutG G be the normal subgroup of Aut G consisting of all elements of Aut G which act trivially on the derived subgroup G of G, and AutG/ζ G,ζ GG be the normal subgroup of Aut G consisting of all central automorphisms of G which also act trivially on the center ζ G of G. Then(i) The extension 1→ Aut_(G') G→ AutG→ Aut(G')→ 1 is split.(ii) Aut_(G') G/Aut_(G/ζ G,ζ G)G≌Sp(2 n, Z) ×(GL(m, Z)■(Z~)m).(iii) Aut_(G/ζ G,ζ GG/Inn G)≌(Z_k)~(2n)⊕(Z)~(2nm).     

G-Identities of Nilpotent Groups. II

The structure of a group V _n,red (G) of reduced G-identities is described subject to the condition that G is a nilpotent group of class 3. We prove the criterion for a G-variety G-var(G) to be finitely based for such G.