Restrictions of Symmetric Invariants of a Complex Semisimple Lie Algebra and Some Applications

Let 𝔤 be a finite-dimensional complex semisimple Lie algebra and σ an arbitrary semisimple automorphism of 𝔤. Let 𝔱 be a Cartan subalgebra of 𝔨 = 𝔤^σ and 𝔥 =Z _𝔤(𝔱) be the centralizer of 𝔱 in 𝔤. Then 𝔥 is a σ-invariant Cartan subalgebra of 𝔤 and 𝔱 = 𝔥^σ. Let W(𝔤, 𝔥) be the Weyl group. One knows that Δ(𝔤, 𝔱), the set of roots of 𝔤 in 𝔱, is also a root system. It is proved that the corresponding Weyl group W(𝔤, 𝔱) is isomorphic to W(𝔤, 𝔥)^σ, which is the subgroup of W(𝔤, 𝔥) consisting of those elements commuting with σ. It is also shown that the image of the restriction map S(𝔥*) ^{W(𝔤, 𝔥)} → S(𝔱*) ^{W(𝔨, 𝔱)}, where S(𝔥*) and S(𝔱*) are the polynomial algebras on 𝔥 and 𝔱, respectively, is exactly S(𝔱*) ^{W(𝔤, 𝔱)}. Based on the above result, we also get a complete classification of the pairs (𝔤, σ) such that 𝔤^σ is noncohomologous to zero in 𝔤.     

Automorphisms Group of an Invariant Subalgebra of a Reductive Lie Algebra

We prove that any automorphism of an invariant subalgebra of a reductive Lie algebra over a field of zero characteristic is a standard automorphism. Mathematics Subject Classifications (2000) 17B20, 17B40.     

A 类量子群和 Hecke 代数的 Schur-Weyl 对偶

设Vm是量子群Uq（SLm)的标准表示,通过Hecke代数的作用,作者将Vm的张量积V^nm分解成了Uq(SLm)的不可约表示的直和,从而给出了Uq(SLm)与Hecke代数的H（q,n)Schur-Weyl对偶的完整证明,进一步得到,当q是实数时,在Hilbert空间H^n上,Uq(SL∞）和H（q,n)之间存在着Schur-Weyl对偶。     

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．     

Classification of graded Hecke algebras for complex reflection groups

The graded Hecke algebra for a finite Weyl group is intimately related to the geometry of the Springer correspondence. A construction of Drinfeld produces an analogue of a graded Hecke algebra for any finite subgroup of GL(V). This paper classifies all the algebras obtained by applying Drinfeld's construction to complex reflection groups. By giving explicit (though nontrivial) isomorphisms, we show that the graded Hecke algebras for finite real reflection groups constructed by Lusztig are all isomorphic to algebras obtained by Drinfeld's construction. The classification shows that there exist algebras obtained from Drinfeld's construction which are not graded Hecke algebras as defined by Lusztig for real as well as complex reflection groups. Received: July 25, 2001     

Young Straightening in a Quotient Sn-Module

We describe a straightening algorithm for the action of S _n on a certain graded ring . The ring appears in the work of C. de Concini and C. Procesi [2] and T. Tanisaki [8], and more recently in the work of A. Garsia and C. Procesi [4]. This ring is a graded version of the permutation representation resulting from the action of S _n on the left cosets of a Young subgroup. As a corollary of our straightening algorithm we obtain a combinatorial proof of the fact that the top degree component of affords the irreducible representation of S _n indexed by .     

Lie Representations and an Algebra Containing Solomon's

We introduce and study a Hopf algebra containing the descent algebra as a sub-Hopf-algebra. It has the main algebraic properties of the descent algebra, and more: it is a sub-Hopf-algebra of the direct sum of the symmetric group algebras; it is closed under the corresponding inner product; it is cocommutative, so it is an enveloping algebra; it contains all Lie idempotents of the symmetric group algebras. Moreover, its primitive elements are exactly the Lie elements which lie in the symmetric group algebras.     

Remarks on Nonassociative Structures in Quantum Projective Field Theory: the Central Extension jl(2,C) of the Double sl(2,C)+sl(2,C) of the Simple Lie Algebra sl(2,C) and Related Topics

This paper is a revised and expanded version of two notes devoted to nonassociative structures in quantum projective field theory.     

Automorphism group and representation of a twisted multi-loop algebra

Let G be the complexification of the real Lie algebra so（3） and A = C[t1^±1, t2^±1] be the Lau-ent polynomial algebra with commuting variables. Let L：（t1, t2, 1） = G c .A be the twisted multi-loop Lie algebra. Recently we have studied the universal central extension, derivations and its vertex operator representations. In the present paper we study the automorphism group and bosonic representations ofL（t1, t2, 1）.     

Types in reductive -adic groups: The Hecke algebra of a cover

In this paper, is a non-Archimedean local field and is the group of -points of a connected reductive algebraic group defined over . Also, is an irreducible representation of a compact open subgroup of , the pair being a type in . The pair is assumed to be a cover of a type in a Levi subgroup of . We give conditions, generalizing those of earlier work, under which the Hecke algebra is the tensor product of a canonical image of and a sub-algebra , for a compact open subgroup of containing .

     

Structure of a Hecke algebra quotient

Let be a Coxeter group with Coxeter graph . Let be the associated Hecke algebra. We define a certain ideal in and study the quotient algebra . We show that when is one of the infinite series of graphs of type , the quotient is semi-simple. We examine the cell structures of these algebras and construct their irreducible representations. We discuss the case where is of type , , or .

     

关于Brunnian辫子群的相对李代数的基

Brunnian辫子群与球面上的同伦群关系密切.在本文中,研究了Brunnian辫子群相对于纯辫子群的相对李代数L^P(Brun_n),通过其与Brunnian辫子群相对于自由群的相对李代数L⁽F_n-1)(Brun_n)的关系,并借助自由群的李代数L(F_n-1)的Hall基给出相对李代数L^P(Brun_n)的基.     

三次可解型非退化李代数及其导子李代数的结构

本文给出了非退化可解李代数的两个类型:三次可解型非退化李代数和扩充的 Heisenberg李代数,并确定三次可解型非退化李代数及其导子李代数的结构．     

量子环面上斜导子李代数的表示

记L为量子环面上的斜导子李代数，本文构造了一族从sl2-模到L-模的函子F^αg，并对L-模F^αg（V）的结构进行了完全刻画，最后给出了L-模F^αg1（V）与F^βg2（W）同构的充分必要条件。     

On the Varieties of Parabolic Subgroups, their Generalizations and Combinatorial Applications

Investigations of homogeneous varieties T=(G:P) of all cosets of finite Coxeter or Chevalley groups G by their maximal parabolic subgroups P had been conducted at the Kalunin seminar at Kiev State University since the 1970s, as were investigations of their corresponding permutation groups, geometries and association schemes.In I. A. Faradev et al. (eds), Investigations in Algebraic Theory of Combinatorial Objects (Kluwer Acad. Publ., 1994), one can find some results on the investigation of noncomplete Galois correspondence between fusion schemes of the orbital scheme for (G,T) and overgroups of (G,T), as well as calculations of the intersectional indices of the Hecke algebra of (G,T). We will discuss additional results on this topic and consider questions related to the following problems: embeddings of varieties (G:P) into the Lie algebra corresponding to Chevalley group G; interpretations of Lie geometries, small Schubert cells, connections between the geometry of G and its associated Weyl geometry in terms of linear algebra, and applications of these problems to calculations performed in Lie geometries and association schemes; constructions of geometric objects arising from Kac–Moody Lie algebras and superalgebras, and applications of these constructions to investigations of graphs of large girth and large size.     

一类无限维半单李代数

研究了秩为2的Witt型的李代数W2的子代数g1,讨论其同态,同构,核的性质.证明了g1为无限维半单李代数.