关于半单李代数的抛物子代数中的一类双极化

本文给出了一种构造复半单李代数抛物子代数中双极化的方法,并给出了其实形式.一般情况下,构造的双极化是非对称的.这种构造方法给出了一大类非可解李代数中极化的例子.后者在表示理论和物理,特别是力学中有重要应用.     

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.     

论实半单李代数的Cartan子代数的内共轭分类

<正> 1.实半单李代数的 Cartan 子代数的共轭分类问题好几位作者曾经讨论过.首先,B.Kostant 在1955年发表了他关于这一问题的讨论的摘要.他从 Cartan 子代数的“向量部分”的讨论出发,得出 Cartan 子代数的共轭分类的初步结果.随后,M.Sugiura 在Kostant 的讨论的基础上,也从“向量部分”的讨论出发得出 Cartan 子代数的共轭分类的完全结果.同年陈仲沪从 Cartan 子代数的“环面部分”的讨论出发,讨论了 Cartan 子代     

半单李代数的单纯作用

本文证明了任何半单李代数(或者李群)在连通光滑流形上的非平凡单纯作用一定没有驻点.而且有效作用的那部分必定是同构于sl(2,R)(或者SL(2,R))的理想.     

关于半单李代数的极大环面子代数的中心化子

本文目的是给出以下命题(见[1])一个简单证明,本文沿用[1]中符号.命题.设 L 是 char=0的代数闭域 F 上的半单李代数,H 是其一极大环面子代数,则 H=C_L(H) (这里 C_L(H) 表示 H 的中心化子).证.分几步进行,记 C=C_L(H).(1)C 包含它的元素的半单部分和幂零部分.对任意 x∈C,有 ad_L xH=0,由[1]命题4.2,(ad_Lx)_sH=0,(ad_L x)H=0.由[1]系理6.4,(ad_Lx)_s=ad_L x_s,(ad_Lx)_n=ad_Lx_n.因此 x_s,x_n∈C.(2)C 的所有半单元均在 H 中.     

关于单李代数的Coxeter-Killing变换

<正> 决定复单李群(代数)的Betti数是个经典的问题.大家知道,它们就是该李群(代数)的Poincare多项式     

半单李代数的一个特征性质

本文给出了中心为零的带非退化对称不变双线性型的有限维李代数的若干性质,并由此给出了半单李代数的一个新刻划。     

一类非Hopf 代数的双Frobenius 代数

本文构造了一类非Hopf 代数的双Frobenius 代数. 特别地, 在某些特殊的情形下, 这里构造的双Frobenius 代数是整体维数为3 的阶1 生成的Artin-Schelter 正则代数的Yoneda 代数.     

实半单李代数的Weyl群及其在极大可解子代数的共轭分类上的应用

<正> 复半单李代数的 Weyl 群在复半单李代数理论中占有极重要的地位.由于复半单李代数的 Cartan 子代数是内共轭的,因此复半单李代数的 Weyl 群的讨论比较简单.熟知,实半单李代数的 Cartan 子代数不一定是内共轭的,而不内共轭的 Cartan 子代数有不同的 Weyl 群.本文的目的就是企图得出实半单李代数的所有不内共轭的 Cartan 子代数的 Weyl 群.由于实半单李代数的 Cartan 子代数的内共轭分类,已被许多作者讨论得非     

Wide Subalgebras of Semisimple Lie Algebras

Let G be a connected semisimple algebraic group over \({\mathbb C}\) , with Lie algebra \({\mathfrak g}\) . Let \({\mathfrak h}\) be a subalgebra of \({\mathfrak g}\) . A simple finite-dimensional \({\mathfrak g}\) -module \({\mathbb V}\) is said to be \({\mathfrak h}\) -indecomposable if it cannot be written as a direct sum of two proper \({\mathfrak h}\) -submodules. We say that \({\mathfrak h}\) is wide, if all simple finite-dimensional \({\mathfrak g}\) -modules are \({\mathfrak h}\) -indecomposable. Some very special examples of indecomposable modules and wide subalgebras appear recently in the literature. In this paper, we describe several large classes of wide subalgebras of \({\mathfrak g}\) and initiate their systematic study. Our approach is based on the study of idempotents in the associative algebra of \({\mathfrak h}\) -invariant endomorphisms of \({\mathbb V}\) . We also discuss a relationship between wide subalgebras and epimorphic subgroups.     

On Limits of Mishchenko--Fomenko Subalgebras in Poisson Algebras of Semisimple Lie Algebras

In this paper, the commutative (with respect to the Poisson bracket) subalgebras in the Poisson algebras of the semisimple Lie algebras are considered on condition that these subalgebras are limits of Mishchenko--Fomenko subalgebras. We study the case of the degeneration within a fixed Cartan subalgebra. The structure of the limit subalgebras is described (i.e., it is proved that these subalgebras are free, and their generators are found). The classification of the limit subalgebras of the above type is also established.     

Pairs of Semisimple Lie Algebras and their Maximal Reductive Subalgebras

Let \(\mathfrak g\) be a semisimple Lie algebra over a field \(\mathbb K\), \(\text{char}\left( \mathbb{K} \right)=0\), and \(\mathfrak g_1\) a subalgebra reductive in \(\mathfrak g\). Suppose that the restriction of the Killing form B of \(\mathfrak g\) to \(\mathfrak g_1 \times \mathfrak g_1\) is nondegenerate. Consider the following statements: ( 1) For any Cartan subalgebra \(\mathfrak h_1\) of \(\mathfrak g_1\) there is a unique Cartan subalgebra \(\mathfrak h\) of \(\mathfrak g\) containing \(\mathfrak h_1\); ( 2) \(\mathfrak g_1\) is self-normalizing in \(\mathfrak g\); ( 3) The B-orthogonal \(\mathfrak p\) of \(\mathfrak g_1\) in \(\mathfrak g\) is simple as a \(\mathfrak g_1\)-module for the adjoint representation. We give some answers to this natural question: For which pairs \((\mathfrak g,\mathfrak g_1)\) do ( 1), ( 2) or ( 3) hold? We also study how \(\mathfrak p\) in general decomposes as a \(\mathfrak g_1\)-module, and when \(\mathfrak g_1\) is a maximal subalgebra of \(\mathfrak g\). In particular suppose \((\mathfrak g,\sigma )\) is a pair with \(\mathfrak g\) as above and σ its automorphism of order m. Assume that \(\mathbb K\) contains a primitive m-th root of unity. Define \(\mathfrak g_1:=\mathfrak g^{\sigma}\), the fixed point algebra for σ. We prove the following generalization of a well known result for symmetric Lie algebras, i.e., for m=2: (a) \((\mathfrak g,\mathfrak g_1)\) satisfies ( 1); (b) For m prime, \((\mathfrak g,\mathfrak g_1)\) satisfies ( 2).     

On Normal Hopf Subalgebras of Semisimple Hopf Algebras

A criterion for subcoalgebras to be invariant under the adjoint action is given generalizing Masuoka’s criterion for normal Hopf subalgebras. At the level of characters, the image of the induction functor from a normal Hopf subalgebra is isomorphic to the image of the restriction functor.     

Linear Commuting Maps on Parabolic Subalgebras of Finite-dimensional Simple Lie Algebras

A map φ on a Lie algebra g is called to be commuting if [φ(x), x] = 0 for all x ∈ g. Let L be a finite-dimensional simple Lie algebra over an algebraically closed field F of characteristic 0, P a parabolic subalgebra of L. In this paper, we prove that a linear mapφon P is commuting if and only if φ is a scalar multiplication map on P.     

On a Class of Finite-dimensional Semisimple Hopf Algebras

Let H be a finite-dimensional and semisimple Hopf algebra over an algebraically closed field of characteristic 0 such that H has exactly one isomorphism class of simple modules that have not dimension 1. These Hopf algebras were the object of study in, for instance, [1 Artamonov , V. A. ( 2007 ). Semisimple finite-dimensional Hopf algebras . Sbornik: Mathematics 198 ( 9 ): 1221 – 1245 .[Crossref], [Web of Science ®] , [Google Scholar]] and [9 Mukhatov , R. B. ( 2009 ). On semisimple finite-dimensional Hopf algebras . Fundamentalnaya i Prikladnaya Matematika 15 ( 2 ): 133 – 143 . [Google Scholar]]. In this paper we study this property in the context of certain abelian extensions of group algebras and give a group theoretical criterion for such Hopf algebras to be of the above type. We also give a classification result in a special case thereof.