Let G be a connected semisimple algebraic group over $k$, with Lie algebra $\g$. Let $\h$ be a subalgebra of $\g$. A simple finite-dimensional $\g$-module V is said to be $\h$-indecomposable if it cannot be written as a direct sum of two proper $\h$-submodules. We say that $\h$ is wide, if all simple finite-dimensional $\g$-modules are $\h$-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 $\g$ and initiate their systematic study. Our approach is based on the study of idempotents in the associative algebra of $\h$-invariant endomorphisms of V. We also discuss a relationship between wide subalgebras and epimorphic subgroups.
Coisotropic Subalgebras of Complex Semisimple Lie Bialgebras
Marco Zambon在他的论文“A Construction for Coisotropic Subalgebras of Lie Bialgebras”中给出了利用复半单李双代数$\mathfrak{g}$的一个长根来构造$\mathfrak{g}$的一个上迷向子代数的方法。本文推广了Zambon的构造。我们的构造是基于$\mathfrak{g}$的二重$\mathfrak{g}\oplus\mathfrak{g}$的拉格朗日子代数的理论，并且我们的上迷向子代数对应于$\mathfrak{g}\oplus\mathfrak{g}$的拉格朗日子代数簇$\mathcal{L}(\mathfrak{g}\oplus\mathfrak{g})$中的环面不动点.
Let $\mathfrak g$ be a semisimple Lie algebra, $\mathfrak h\subset\mathfrak g$ a reductive subalgebra such that $\mathfrak h^\perp$ is a complementary $\mathfrak h$-submodule of $\mathfrak g$. In 1983, Bogoyavlenski claimed that one obtains a Poisson commutative subalgebra of the symmetric algebra ${\mathcal S}(\mathfrak g)$ by taking the subalgebra ${\mathcal Z}$ generated by the bi-homogeneous components of all $H\in{\mathcal S}(\mathfrak g)^{\mathfrak g}$. But this is false, and we present a counterexample. We also provide a criterion for the Poisson commutativity of such subalgebras ${\mat…
We study {\em disemisimple} Lie algebras, i.e., Lie algebras which can be written as a vector space sum of two semisimple subalgebras. We show that a Lie algebra $\mathfrak{g}$ is disemisimple if and only if its solvable radical coincides with its nilradical and is a prehomogeneous $\mathfrak{s}$-module for a Levi subalgebra $\mathfrak{s}$ of $\mathfrak{g}$. We use the classification of prehomogeneous $\mathfrak{s}$-modules for simple Lie algebras $\mathfrak{s}$ given by Vinberg to show that the solvable radical of a disemisimple Lie algebra with simple Levi subalgebra is abelian. We extend th…
Maximal subalgebras of the exceptional Lie algebras in low characteristic
本文研究了正特征代数闭域中例外李代数的极大子代数。这首先是一个快速回顾的文章由Herpel和斯图尔特认为Cartan型极大子代数在例外的李代数的良好特性，然后文章由Premet考虑非半单极大子代数的良好特性。对于$p=5$，我们给出了一个例子，似乎是一个新的极大子代数中的例外李代数类型$E_8$。证明了该极大子代数同构于非限制Witt代数$W(1;2)$的$p$ -闭包.在此之后，我们完全集中在特征$p=2$和$p=3$给出的例子，新的非半单极大子代数的例外李代数。我们认为Weisfeiler过滤与这些极大子代数，留下许多悬而未决的问题。在$F_4$ for $p=3$和$E_8$ for $p=2$中有一两个简单极大子代数的例子。
We study a semisimple extension of a Takiff superalgebra which turns out to have a remarkably rich representation theory. We determine the blocks in both the finite-dimensional and BGG module categories and also classify the Borel subalgebras. We further compute all extension groups between two finite-dimensional simple objects and prove that all non-principal blocks in the finite-dimensional module category are Koszul.
We find the normal form of nilpotent elements in semisimple Lie algebras that generalizes the Jordan normal form in $\mathfrak{sl}_N$, using the theory of cyclic elements.
We classify filtered quantizations of conical symplectic singularities and use this to show that all filtered quantizations of symplectic quotient singularities are spherical Symplectic reflection algebras of Etingof and Ginzburg. We further apply our classification and a classification of filtered Poisson deformations obtained by Namikawa to establish a version of the Orbit method for semisimple Lie algebras. Namely, we produce a natural map from the set of adjoint orbits in a semisimple Lie algebra to the set of primitive ideals in the universal enveloping algebra. We show that the map is in…
Let $\mathfrak{g}$ be a finite-dimensional semisimple complex Lie algebra and $θ$ an involutive automorphism of $\mathfrak{g}$. According to G. Letzter, S. Kolb and M. Balagović the fixed-point subalgebra $\mathfrak{k} = \mathfrak{g}^θ$ has a quantum counterpart $B$, a coideal subalgebra of the Drinfeld-Jimbo quantum group $U_q(\mathfrak{g})$ possessing a universal K-matrix $\mathcal{K}$. The objects $θ$, $\mathfrak{k}$, $B$ and $\mathcal{K}$ can all be described in terms of Satake diagrams. In the present work we extend this construction to generalized Satake diagrams, combinatorial data firs…
There exist principal $\mathfrak{sl}_2$ subalgebras for hyperbolic Kac-Moody Lie algebras. In the case of rank 2 symmetric hyperbolic Kac-Moody Lie algebras, certain $\mathfrak{sl}_2$ subalgebras are constructed. These subalgebras are generalizations of principal $\mathfrak{sl}_2$ subalgebras. We show that the rank 2 symmetric hyperbolic Kac-Moody Lie algebras themselves are irreducibly decomposed under the action of this $\mathfrak{sl}_2$ subalgebras. Furthermore, we classify irreducible components of the decomposition. In particular, we obtain multiplicities of unitary principal series and c…
