Composition factors of Kac-modules for the general linear Lie superalgebras $gl_{m|n}$

A new characterization of Kac-Moody-Malcev superalgebras

In the past two decades there has been a great attention to Lie (super)algebras which are extensions of affine Kac-Moody Lie (super)algebras, in certain typical or axiomatic approaches. These Lie (super)algebras have been mostly studied under variations of the name "extended affine Lie (super)algebras". We show that certain classes of Malcev (super)algebras also can be put in this framework. This in particular allows to provide new examples of Malcev (super)algebras which extend the known Kac-Moody Malcev (super)algebras.

Crystal bases of q-deformed Kac modules over the quantum superalgebra $U_q(\gl(m|n))$

We introduce the notion of a crystal base of a finite dimensional q-deformed Kac module over the quantum superalgebra $U_q(\gl(m|n))$, and prove its existence and uniqueness. In particular, we obtain the crystal base of a finite dimensional irreducible $U_q(\gl(m|n))$-module with typical highest weight. We also show that the crystal base of a q-deformed Kac module is compatible with that of its irreducible quotient $V(λ)$ given by Benkart, Kang and Kashiwara when $V(λ)$ is an irreducible polynomial representation.

A Borcherds-Kac-Moody superalgebra with Conway symmetry

We construct a Borcherds Kac-Moody (BKM) superalgebra on which the Conway group Co$_0$ acts faithfully. We show that the BKM algebra is generated by the BRST-closed states in a chiral superstring theory. We use this construction to produce denominator identities for the chiral partition functions of the Conway module $V^{s\natural}$, a supersymmetric $c=12$ chiral conformal field theory whose (twisted) partition functions enjoy moonshine properties and which has automorphism group isomorphic to Co$_0$. In particular, these functions satisfy a genus zero property analogous to that of monstrous …

Local Weyl modules and fusion products for the current superalgebra $\mathfrak{sl}(1|2)[t]$

We study a class of modules, called Chari-Venkatesh modules, for the current superalgebra $\mathfrak{sl}(1|2)[t]$. This class contains other important modules, such as graded local Weyl, truncated local Weyl and Demazure-type modules. We prove that Chari-Venkatesh modules can be realized as fusion products of generalized Kac modules. In particular, this proves Feigin and Loktev's conjecture, that fusion products are independent of their fusion parameters in the case where the fusion factors are generalized Kac modules. As an application of our results, we obtain bases, dimension and character …

Representations of affine Lie superalgebras and their quantization in type A

We construct a new family of irreducible modules over any basic classical affine Kac-Moody Lie superalgebra which are induced from modules over the Heisenberg subalgebra. We also obtain irreducible deformations of these modules for the quantum affine superalgebra of type A.

Generalised Jantzen filtration of Lie superalgebras I

A Jantzen type filtration for generalised Varma modules of Lie superalgebras is introduced. In the case of type I Lie superalgebras, it is shown that the generalised Jantzen filtration for any Kac module is the unique Loewy filtration, and the decomposition numbers of the layers of the filtration are determined by the coefficients of inverse Kazhdan-Lusztig polynomials. Furthermore, the length of the Jantzen filtration for any Kac module is determined explicitly in terms of the degree of atypicality of the highest weight. These results are applied to obtain a detailed description of the submod…

Representations of Lie superalgebras in prime characteristic III

For a restricted Lie superalgebra g over an algebraically closed field of characteristic p > 2, we generalize the deformation method of Premet and Skryabin to obtain results on the p-power and 2-power divisibility of dimensions of g-modules. In particular, we give a new proof of the Super Kac-Weisfeiler conjecture for basic classical Lie superalgebras. The new proof allows us to improve optimally the assumption on p. We also establish a semisimplicity criterion for the reduced enveloping superalgebras associated with semisimple p-characters for all basic classical Lie superalgebras using the t…

Minimal W-superalgebras and modular representations of basic Lie superalgebras

Let $\mathfrak{g}=\mathfrak{g}_{\bar 0}+\mathfrak{g}_{\bar 1}$ be a basic Lie superalgebra over $\mathbb{C}$, and $e$ a minimal nilpotent element in $\mathfrak{g}_{\bar 0}$. Set $W_χ'$ to be the refined $W$-superalgebra associated with the pair $(\mathfrak{g},e)$, which is called a minimal $W$-superalgebra. In this paper we present a set of explicit generators of minimal $W$-superalgebras and the commutators between them. In virtue of this, we show that over an algebraically closed field $\mathds{k}$ of characteristic $p\gg0$, the lower bounds of dimensions in the modular representations of ba…

Cohomology of Lie superalgebras $sl_{m|n}$ and $osp_{2|2n}$

We explicitly compute the first and second cohomology groups of the classical Lie superalgebras $sl_{m|n}$ and $osp_{2|2n}$ with coefficients in the finite dimensional irreducible modules and the Kac modules. We also show that the second cohomology groups of these Lie superalgebras with coefficients in the respective universal enveloping algebras (under the adjoint action) vanish. The latter result in particular implies that the universal enveloping algebras $U(sl_{m|n})$ and $U(osp_{2|2n})$ do not admit any non-trivial formal deformations of Gerstenhaber type.

Representations of Lie Superalgebras in Prime Characteristic I

We initiate the representation theory of restricted Lie superalgebras over an algebraically closed field of characteristic p>2. A superalgebra generalization of the celebrated Kac-Weisfeiler Conjecture is formulated, which exhibits a mixture of p-power and 2-power divisibilities of dimensions of modules. We establish the Conjecture for basic classical Lie superalgebras.

Modules Over Affine Lie Superalgebras

Modules over affine Lie superalgebras ${\cal G}$ are studied, in particular, for ${\cal G}=\hat{OSP(1,2)}$. It is shown that on studying Verma modules, much of the results in Kac-Moody algebra can be generalized to the super case. Of most importance are the generalized Kac-Kazhdan formula and the Malikov-Feigin-Fuchs construction, which give the weights and the explicit form of the singular vectors in the Verma module over affine Kac-Moody superalgebras. We have also considered the decomposition of the admissible representation of $\hat{OSP(1,2)}$ into that of $\hat{SL(2)}\otimes$Virasoro alge…

Typical Irreducible Characters of Generalized Quantum Groups

We introduce the definition of the typical irreducible modules of the generalized quantum groups, and prove the Weyl-Kac-type formulas of their characters. As a by-product, we obtain the Weyl-Kac-type character formulas of the typical irreducible modules of the quantum superalgebras associated with the basic classical Lie superalgebras, which is explained in Introduction.

量子超代数 $U_q(\mathfrak{gl}(m|n))$ 负半部分的晶基

Crystal base of the negative half of the quantum superalgebra $U_q(\mathfrak{gl}(m|n))$

本文构建了量子超代数 $U_q(\mathfrak{gl}(m|n))$ 负半部分的晶基，并给出了其关联晶 $\mathscr{B}_{m|n}(\infty)$ 的组合描述，同时研究了晶基与Kac模块之间的兼容性。

Highest weight vectors of mixed tensor products of general linear Lie superalgebras

In this paper, a notion of cyclotomic (or level $k$) walled Brauer algebras $\mathscr B_{k, r, t}$ is introduced for arbitrary positive integer $k$. It is proven that $\mathscr B_{k, r, t}$ is free over a commutative ring with rank $k^{r+t}(r+t)!$ if and only if it is admissible. Using super Schur-Weyl duality between general linear Lie superalgebras $\mathfrak{gl}_{m|n}$ and $\mathscr B_{2, r, t}$, we give a classification of highest weight vectors of $\mathfrak{gl}_{m|n}$-modules $M_{pq}^{rt}$, the tensor products of Kac-modules with mixed tensor products of the natural module and its dual. …

Kazhdan-Lusztig polynomials and character formulae for the Lie superalgebra gl(m|n)

The problem of computing the characters of the finite dimensional irreducible representations of the Lie superalgebra $\mathfrak{gl}(m|n)$ over $\C$ was solved a few years ago by V. Serganova. In this article, we present an entirely different approach. One consequence is a direct and elementary proof of a conjecture made by van der Jeugt and Zhang for the composition multiplicities of Kac modules. This does not seem to follow easily from Serganova's formula, since that involves certain alternating sums. We also compute Ext's between simple modules in the category of finite dimensional represen…

N=1 BMS 超代数的奇异向量、特征标与合成列

Singular vectors, characters, and composition series for the N=1 BMS superalgebra

本文研究了 N=1 BMS 超代数上 Verma 模的结构，分类了奇异向量，揭示了极大子模结构与合成列，推导了不可约最高权模的特征标公式，并确定了 W(2,2) 代数上的相关结构。

Generators and relations for (generalised) Cartan type superalgebras

In Kac's classification of finite-dimensional Lie superalgebras, the contragredient ones can be constructed from Dynkin diagrams similar to those of the simple finite-dimensional Lie algebras, but with additional types of nodes. For example, $A(n-1,0) = \mathfrak{sl}(1|n)$ can be constructed by adding a "gray" node to the Dynkin diagram of $A_{n-1} = \mathfrak{sl}(n)$, corresponding to an odd null root. The Cartan superalgebras constitute a different class, where the simplest example is $W(n)$, the derivation algebra of the Grassmann algebra on $n$ generators. Here we present a novel construct…

通过张量范畴从八元数到复合超代数

From octonions to composition superalgebras via tensor categories

本文通过特征3循环群表示的对称张量范畴的半简化过程，从分裂Cayley代数及其3阶自同构获得仅存在于特征3的3维和6维非平凡含幺复合超代数，并讨论其与扩展Freudenthal魔方及例外Lie超代数的联系。

Extremal projectors for contragredient Lie (super)symmetries (short review)

A brief review of the extremal projectors for contragredient Lie (super)symmetries (finite-dimensional simple Lie algebras, basic classical Lie superalgebras, infinite-dimensional affine Kac-Moody algebras and superalgebras, as well as their quantum $q$-analogs) is given. Some bibliographic comments on the applications of extremal projectors are presented.

Vertex Operator Superalgebras and Their Representations

After giving some definitions for vertex operator SUPERalgebras and their modules, we construct an associative algebra corresponding to any vertex operator superalgebra, such that the representations of the vertex operator algebra are in one-to-one correspondence with those of the corresponding associative algebra. A way is presented to decribe the fusion rules for the vertex operator superalgebras via modules of the associative algebra. The above are generalizations of Zhu's constructions for vertex operator algebras. Then we deal in detail with vertex operator superalgebras corresponding to …

Tensor hierarchy algebras and extended geometry I: Construction of the algebra

Tensor hierarchy algebras constitute a class of non-contragredient Lie superalgebras, whose finite-dimensional members are the "Cartan-type" Lie superalgebras in Kac's classification. They have applications in mathematical physics, especially in extended geometry and gauged supergravity. We further develop the recently proposed definition of tensor hierarchy algebras in terms of generators and relations encoded in a Dynkin diagram (which coincides with the diagram for a related Borcherds superalgebra). We apply it to cases where a grey node is added to the Dynkin diagram of a rank $r+1$ Kac-Mo…

Fun with $F_{24}$

We study some special features of $F_{24}$, the holomorphic $c=12$ superconformal field theory (SCFT) given by 24 chiral free fermions. We construct eight different Lie superalgebras of "physical" states of a chiral superstring compactified on $F_{24}$, and we prove that they all have the structure of Borcherds-Kac-Moody superalgebras. This produces a family of new examples of such superalgebras. The models depend on the choice of an $\mathcal{N}=1$ supercurrent on $F_{24}$, with the admissible choices labeled by the semisimple Lie algebras of dimension 24. We also discuss how $F_{24}$, with a…

泊松超代数的Shapovalov行列式

The Shapovalov determinant for the Poisson superalgebras

本研究针对几类无Cartan矩阵但含二次偶Casimir元C₂的单Z阶李超代数及相关泊松超代数，利用C₂计算其Shapovalov行列式，并将A. Shapovalov的不可约表示结果推广到Verma模，给出不可约性判据。

仿射李代数的双曲化

Hyperbolization of Affine Lie Algebras

本文通过分类双曲Borcherds–Kac–Moody超代数，证明了恰有81个仿射李代数可扩张为双曲BKM超代数，并厘清了它们与全纯共形场论结构及模形式的关系。

一个可容许水平的 $\widehat{\mathfrak{osp}} \left( 1 \middle\vert 2 \right)$-模型：模变换与 Verlinde 公式

An admissible level $\widehat{\mathfrak{osp}} \left( 1 \middle\vert 2 \right)$-model: modular transformations and the Verlinde formula

本文研究水平为 -5/4 的仿射 osp(1|2) 顶点算子超代数的模性质，通过分类 relaxed 最高权模并利用 Verlinde 公式的连续超代数类比，得到全部 Grothendieck 融合规则且系数均为非负整数。