Some representations of nongraded Lie algebras of generalized Witt type

Simple Lie algebras which generalize Witt algebras

We introduce a new class of simple Lie algebras $W(n,m)$ that generalize the Witt algebra by using "exponential" functions, and also a subalgebra $W^*(n,m)$ thereof; and we show each derivation of $W^*(1,0)$ can be written as a sum of an inner derivation and a scalar derivation. The Lie algebra $W(n,m)$ is $Z$-graded and is infinite growth.

Classification of Simple Cuspidal Modules over a Lattice Lie Algebra of Witt type

Let $W_π$ be the lattice Lie algebra of Witt type associated with an additive inclusion $π: \mathbb{Z}^N \hookrightarrow \mathbb{C}^2$ with $N>1$. In this article, the classification of simple $\mathbb{Z}^N$-graded $W_π$-modules, whose multiplicities are uniformly bounded, is given.

On structure of graded restricted simple Lie algebras of Cartan type as modules over the Witt algebra

Any graded restricted simple Lie algebra of Cartan type contains a subalgebra isomorphic to the Witt algebra over a field of prime characteristic. As some analogue of study on branching rules for restricted non-classical Lie algebras, it is shown that each graded restricted simple Lie algebra of Cartan type can be decomposed into a direct sum of restricted baby Verma modules and simple modules as an adjoint module over the Witt algebra. In particular, the composition factors are precisely determined.

多项式代数上的仿射Nappi-Witten李代数的表示

Representations of affine Nappi-Witten Lie algebras over polynomial algebras

本文分类了Nappi-Witten李代数H4及其仿射代数上的秩一Cartan自由模，给出了不可约充要条件，并应用于仿射-Virasoro Nappi-Witten李代数。

Brackets with $(τ,σ)$-derivations and $(p,q)$-deformations of Witt and Virasoro algebras

The aim of this paper is to study some brackets defined on $(τ,σ)$-derivations satisfying quasi-Lie identities. Moreover, we provide examples of $(p,q)$-deformations of Witt and Virasoro algebras as well as $\mathfrak{sl}(2)$ algebra. These constructions generalize the results obtained by Hartwig, Larsson and Silvestrov on $σ$-derivations, arising in connection with discretizations and deformations of algebras of vector fields.

On Cachazo-Douglas-Seiberg-Witten conjecture for simple Lie algebras

We give a uniform proof of a significant part of the Cachazo-Douglas-Seiberg-Witten conjecture by using topology and geometry of infinite Grassmannians.

A Poincaré-Birkhoff-Witt Theorem for profinite pronilpotent Lie algebras

We prove a version of the Poincaré-Birkhoff-Witt Theorem for profinite pronilpotent Lie algebras in which their symmetric and universal enveloping algebras are replaced with appropriate formal analogues and discuss some immediate corollaries of this result.

Whittaker modules for the twisted affine Nappi-Witten Lie algebra $\widehat{H}_{4}[τ]$

The Whittaker module $M_ψ$ and its quotient Whittaker module $L_{ψ, ξ}$ for the twisted affine Nappi-Witten Lie algebra $\widehat{H}_{4}[τ]$ are studied. For nonsingular type, it is proved that if $ξ\neq 0$, then $L_{ψ,ξ}$ is irreducible and any irreducible Whittaker $\widehat{H}_{4}[τ]$-module of type $ψ$ with ${\bf k}$ acting as a non-zero scalar $ξ$ is isomorphic to $L_{ψ,ξ}$. Furthermore, for $ξ=0$, all Whittaker vectors of $L_{ψ, 0}$ are completely determined. For singular type, the Whittaker vectors of $L_{ψ, ξ}$ with $ξ\neq 0$ are fully characterized.

Witt与Virasoro代数上的分次反pre-Lie代数结构

Graded anti-pre-Lie algebraic structures on Witt and Virasoro algebras

本文通过分类Witt代数的不可分解权表示，给出了其上的分次反pre-Lie代数结构及同构分类，并证明了Virasoro代数上不存在满足自然条件的此类结构。

有限截断当前李代数上的简单模

Simple modules over truncated current Lie algebras of the Witt algebra

本文研究了有限截断当前李代数W_ℓ上p-特征为χ且高度不超过1的简单模，并给出其分类；进一步探讨了p-特征高度大于1的简单模家族。

B扭曲Gaiotto-Witten理论与拓扑量子场论

B-twisted Gaiotto-Witten theory and topological quantum field theory

本研究发展表示论技术，基于李超代数展开量化的权模范畴相对模结构，构造三维非半单拓扑量子场论，建模含线性物质的阿贝尔Gaiotto-Witten理论的同调截断拓扑B扭曲，纳入非真实线算子，涵盖多类Chern-Simons相关理论特例。

Cohomology of Hom-Lie superalgebras and q-deformed Witt superalgebra

The purpose of this paper is to define the representation and the cohomology of Hom-Lie superalgebras. Moreover we study Central extensions and provide as application the computations of the derivations and second cohomology group of q-deformed Witt superalgebra.

Restricted Cohomology of Modular Witt Algebras

We classify one-dimensional restricted central extensions of the modular Witt Lie algebra in characteristic $p>3$.

On the Cachazo-Douglas-Seiberg-Witten conjecture for simple Lie algebras, II

Recently, motivated by supersymmetric gauge theory, Cachazo, Douglas, Seiberg, and Witten proposed a conjecture about finite dimensional simple Lie algebras, and checked it in the classical cases. Later V. Kac and the author proposed a uniform approach to this conjecture, based on the theory of abelian ideals in the Borel subalgebra; this allowed them to check the conjecture for type G_2. In this note we further develop this approach, and propose three natural conjectures which imply the three parts of the CDSW conjecture. In a sense, these conjectures explain why the CDSW conjecture should be…

Witt 李代数的多项式表示

Polynomial representations of the Witt Lie algebra

本文研究 Witt 李代数的多项式表示，证明有限生成表示是诺特的且具有有理 Hilbert 级数，并建立其与有限集合范畴及自同态幺半群表示的等价性，作为 Operad 化 Schur–Weyl 对偶的特例。

Witt代数在分类量子群上的作用

Action of the Witt algebra on categorified quantum groups

本文构建了正Witt代数在简单李代数分类量子群上的作用，并在A型情况恢复了Qi等人对gl_n泡沫的作用，同时证明该构造与迹去分类兼容，诱导出在电流代数上的作用。

Lie algebras in symmetric monoidal categories

We study algebras defined by identities in symmetric monoidal categories. Our focus is on Lie algebras. Besides usual Lie algebras, there are examples appearing in the study of knot invariants and Rozansky-Witten invariants. Our main result is a proof of Westbury's conjecture for K3-surface: there exists a Lie algebra homomorphism from Vogel's universal simple Lie algebra to the Lie algebra describing the Rozansky-Witten invariants of a K3-surface. Most of the paper involves setting up a proper language to discuss the problem and we formulate nine open questions as we proceed.

Infinite Dimensional 3-Lie Algebras and Their Connections to Harish-Chandra Modules

In this paper we construct two kinds of infinite-dimensional 3-Lie algebras from a given commutative associative algebra, and show that they are all canonical Nambu 3-Lie algebras. We relate their inner derivation algebras to Witt algebras, and then study the regular representations of these 3-Lie algebras and the natural representations of the inner derivation algebras. In particular, for the second kind of 3-Lie algebras, we find that their regular representations are Harish-Chandra modules, and the inner derivation algebras give rise to intermediate series modules of the Witt algebras and c…

Filtering bases and cohomology of nilpotent subalgebras of Witt and $\widetilde{sl}_2$ Lie algebras

We study the cohomology with trivial coefficients of Lie algebras L_k of the polynomial vector fields on the line with zero $k$-jet, (k>=1), and the cohomology of the similar subalgebras {L}_k of the polynomial loops algebra $\widetilde{sl}_2$. In both cases we construct the special bases (filtering bases) in the external complexes of these algebras. A spectral sequence based on this construction allows to completely find the cohomology of L_k and {L}_k. We also apply the filtering bases to find the spectral resolution of the Laplace operators for algebras L_1 and L_0, and obtain explicit form…

Central extensions, derivations, and automorphisms of semi-direct sums of the Witt algebra with its intermediate series modules

Lie algebras formed via semi-direct sums of the Witt algebra $\text{Der}(\mathbb{C}[t,t^{-1}])$ and its modules have become increasingly prominent in both physics and mathematics in recent years. In this paper, we complete the study of (Leibniz) central extensions, derivations and automorphisms of the Lie algebras formed from the semi-direct sum of the Witt algebra and its indecomposable intermediate series modules (that is, graded modules with one-dimensional graded components). Our techniques exploit the internal grading of the Witt algebra, which can be applied to a wider class of graded Li…

Derived Poincaré-Birkhoff-Witt theorems (with an appendix by Vladimir Dotsenko)

We define derived Poincaré--Birkhoff--Witt maps of dg operads or derived PBW maps, for short, which extend the definition of PBW maps between operads of V.~Dotsenko and the second author in 1804.06485, with the purpose of studying the universal enveloping algebra of dg Lie algebras as a functor on the homotopy category. Our main result shows that the map from the homotopy Lie operad to the homotopy associative operad is derived PBW, which gives us an amenable description of the homology of the universal envelope of an $L_\infty$-algebra in the sense of Lada--Markl. We deduce from this several …

Poincare-Birkhoff-Witt expansions of the canonical elliptic differential form

We study the canonical U(\n)-valued elliptic differential form, whose projections to different Kac-Moody algebras are key ingredients of the hypergeometric integral solutions of elliptic KZ differential equations and Bethe ansatz constructions. We explicitly determine the coefficients of the projections in the simple Lie algebras A_r, B_r, C_r, D_r in a conveniently chosen Poincare-Birkhoff-Witt basis. As an application we give a new formula for eigenfunctions of Hamiltonians of the Calogero-Moser model.

Irreducible Witt modules from Weyl modules and $\mathfrak{gl}_{n}$-modules

For an irreducible module $P$ over the Weyl algebra $\mathcal{K}_n^+$ (resp. $\mathcal{K}_n$) and an irreducible module $M$ over the general liner Lie algebra $\mathfrak{gl}_n$, using Shen's monomorphism, we make $P\otimes M$ into a module over the Witt algebra $W_n^+$ (resp. over $W_n$). We obtain the necessary and sufficient conditions for $P\otimes M$ to be an irreducible module over $W_n^+$ (resp. $W_n$), and determine all submodules of $P\otimes M$ when it is reducible. Thus we have constructed a large family of irreducible weight modules with many different weight supports and many irred…

On Weakly Complete Universal Enveloping Algebras: A Poincare-Birkhoff-Witt Theorem

We study universal enveloping Hopf algebras of Lie algebras in the category of weakly complete vector spaces over the real and complex field.

Non-weight representations of Cartan type S Lie algebras

For the two Cartan type S subalgebras of the Witt algebra $\W_n$, called Lie algebras of divergence-zero vector fields, we determine all module structures on the universal enveloping algebra of their Cartan subalgebra $\h_n$. We also give all submodules of these modules.

Singular Virasoro vectors and Lie algebra cohomology

We present an explicit formula for a new family of Virasoro singular vectors. As a corrolary we get formulas for differentials of Feigin-Fuchs-Rocha-Carridi-Wallach resolution of the the positive nilpotent part of Virasoro (or Witt) algebra $L_1$.

Simple weight modules with finite-dimensional weight spaces over Witt superalgebras

Let $A_{m,n}$ be the tensor product of the Laurient polynomial algebra in $m$ even variables and the exterior algebra in $n$ odd variables over the complex field $\bC$, and the Witt superalgebra $W_{m,n}$ be the Lie superalgebra of superderivations of $A_{m,n}$. In this paper, we classify the simple weight $W_{m,n}$ modules with finite-dimensional weight spaces with respect to the standard Cartan algebra of $W_{m,0}$. Every such module is either a simple quotient of a tensor module or a module of highest weight type.

Nilpotent commuting varieties of the Witt algebra

Let $\mathfrak{g}$ be the $p$-dimensional Witt algebra over an algebraically closed field $k$ of characteristic $p>3$. Let $\mathscr{N}={x\in\ggg\mid x^{[p]}=0}$ be the nilpotent variety of $\mathfrak{g}$, and $\mathscr{C}(\mathscr{N}):=\{(x,y)\in \mathscr{N}\times\mathscr{N}\mid [x,y]=0\}$ the nilpotent commuting variety of $\mathfrak{g}$. As an analogue of Premet's result in the case of classical Lie algebras [A. Premet, Nilpotent commuting varieties of reductive Lie algebras. Invent. Math., 154, 653-683, 2003.], we show that the variety $\mathscr{C}(\mathscr{N})$ is reducible and equidimens…

高阶代数中的 Poincaré-Birkhoff-Witt 定理

Poincaré-Birkhoff-Witt Theorems in Higher Algebra

本文将经典的 Poincaré-Birkhoff-Witt 定理扩展至高阶代数，通过揭示谱中算畴及不同 $\mathbb{E}_n$-算畴间的基本关系，证明了适用于谱李代数及 $\mathbb{E}_n$-代数相对包络代数的定理变体，并给出了高阶包络代数的简单构造。

系数在模的张量积中的 Witt 代数的 1-上循环

1-cocycles of the Witt algebra with coefficients in tensor product of modules

本文分类系数在两个任意张量密度模张量积中的 Witt 代数 1-上循环，恢复 Ng–Taft 定理，并据此确定若干含 Witt 代数的无限维李代数的李双代数结构。

Supports of weight modules over Witt algebras

In this paper, as the first step towards classification of simple weight modules with finite dimensional weight spaces over Witt algebras $W_n$, we explicitly describe supports of such modules. We also obtain some descriptions on the support of an arbitrary simple weight module over a $\Z^n$-graded Lie algebra $\mathfrak{g}$ having a root space decomposition $\oplus_{α\in\Z^n}\mathfrak {g}_α$ with respect to the abelian subalgebra $\mathfrak {g}_0$, with the property $[\mathfrak{g}_α,\mathfrak {g}_β]= \mathfrak {g}_{α+β}$ for all $α,β\in\Z^n$, $α\neq β$ (this class contains the algebra $W_n$).

Z2 and Klein graded Lie algebras

In this master's thesis, we recall the definitions and basic results for Lie superalgebras. We specify the definition for Klein graded Lie algebras and, motivated by well known results for Lie superalgebras, we prove similar results for Klein graded Lie algebras. More precisely, we state the theorems of Poincare-Birkhoff-Witt and Ado's, as well as Schur's lemma. Moreover, we present two examples of Klein graded algebra.

Universal representations of Lie algebras by coderivations

A class of representations of a Lie superalgebra (over a commutative superring) in its symmetric algebra is studied. As an application we get a direct and natural proof of a strong form of the Poincare'-Birkhoff-Witt theorem, extending this theorem to a class of nilpotent Lie superalgebras. Other applications are presented. Our results are new already for Lie algebras.

Tensor modules over Witt superalgebras

In this paper, we study the tensor module $P\otimes M$ over the Witt superalgebra $W_{m,n}^+$ (resp. $W_{m,n}$), where $P$ is a simple module over the Weyl superalgebra $K_{m,n}^+$ (resp. $K_{m,n}$) and $M$ is simple weight module over the general linear Lie superalgebra $\mathfrak{gl}(m,n)$. We obtain the necessary and sufficient conditions for $P\otimes M$ to be simple, and determine all simple subquotient of $P\otimes M$ when it is not simple. All the work leads to completion of some classification problems on the weight representation theory of $W_{m,n}^+$ and $W_{m,n}$.

Lie subalgebras of Differential Operators in one Variable

Let $\operatorname{Witt}$ be the Lie algebra generated by the set $\{L_i\,\vert\, i \in {\mathbb Z}\}$ and $\operatorname{Vir}$ its universal central extension. Let $\operatorname{Diff}(V)$ be the Lie algebra of differential operators on $V=\mathbb{C}[[z]]$, $\mathbb{C}((z))$ or $V=\mathbb{C}(z)$. We explicitly describe all Lie algebra homomorphisms from $\mathfrak{sl}(2)$, $\operatorname{Witt}$ and $\operatorname{Vir}$ to $\operatorname{Diff}(V)$ such that $L_0$ acts on $V$ as a first order differential operator.

Irreducible weight modules over Witt algebras with infinite dimensional weight spaces

Let $d>1$ be an integer. In 1986, Shen defined a class of weight modules $F^α_b(V)$ over the Witt algebra $\mathcal{W}_d$ for $\a\in\C^d$, $b\in\C$, and an irreducible module $ V$ over the special linear Lie algebra $\sl_d$. In 1996, Eswara Rao determined the necessary and sufficient conditions for these modules to be irreducible when $V$ is finite dimensional. In this note, we will determine the necessary and sufficient conditions for all these modules $F^α_b(V)$ to be irreducible where $V$ is not necessarily finite dimensional. Therefore we obtain a lot of irreducible $\mathcal{W}_d$-modules…

On a family of non-weight modules over Virasoro-type Lie (super)algebras

In this thesis we classify modules over a Witt-type Lie algebra and superalgebra such that when considered as modules of $\mathcal{U}(\mathfrak{h})$ they are free of rank 1. We provide sufficient conditions for simplicity, and compute the action of an automorphism on the module. Lastly, we apply the weighting functor and show that the resulting modules are intermediate series modules.

An elementary proof of the vanishing of the second cohomology of the Witt and Virasoro algebra with values in the adjoint module

By elementary and direct calculations the vanishing of the (algebraic) second Lie algebra cohomology of the Witt and the Virasoro algebra with values in the adjoint module is shown. This yields infinitesimal and formal rigidity or these algebras. The first (and up to now only) proof of this important result was given 1989 by Fialowski in an unpublished note. It is based on cumbersome calculations. Compared to the original proof the presented one is quite elegant and considerably simpler.

Borel subalgebras of the Witt algebra $W_1$

Let $\mathbb{F}$ be an algebraically closed field of characteristic $p>3$, and $\ggg$ the $p$-dimensional Witt algebra over $\mathbb{F}$. Let $\N$ be the nilpotent cone of $\ggg$. Explicit description of $\N$ is given, so that the conjugacy classes of Borel subalgebras of $\ggg$ under the automorphism group are determined. In contrast with only one conjugacy class of Borel subalgebras in a classical simple Lie algebra, there are two conjugacy classes of Borel subalgebras in $\ggg$. The representatives of conjugacy classes of Borel subalgebras, i.e., the so-called standard Borel subalgebras, ar…

A remark on cohomology of nilpotent Lie algebras

We prove that the cohomology algebra of a conilpotent Lie coalgebra is generated in degree 1 as an A-infinity algebra. By dualizing, the same is true about cohomology algebras of finite dimensional nilpotent Lie algebras. In the process, we provide a proof of the conilpotent version of the dual Poincare-Birkhoff-Witt theorem.

Classification of the maximal subalgebras of exceptional Lie algebras over fields of good characteristic

Let $G$ be an exceptional simple algebraic group over an algebraically closed field $k$ and suppose that the characteristic $p$ of $k$ is a good prime for $G$. In this paper we classify the maximal Lie subalgebras $\mathfrak{m}$ of the Lie algebra $\mathfrak{g}={\rm Lie}(G)$. Specifically, we show that one of the following holds: $\mathfrak{m}={\rm Lie}(M)$ for some maximal connected subgroup $M$ of $G$, or $\mathfrak{m}$ is a maximal Witt subalgebra of $\mathfrak{g}$, or $\mathfrak{m}$ is a maximal $\it{\mbox{exotic semidirect product}}$. The conjugacy classes of maximal connected subgroups o…