Double Koszul Complex and Construction of Irreducible Representations of $\frak{gl}(3|1)$

Jacobi-Trudi type formula for a class of irreducible representations of $\frak{gl}(m|n)$

We prove a determinantal type formula to compute the characters for a class of irreducible representations of the general Lie superalgebra $\mathfrak{gl}(m|n)$ in terms of the characters of the symmetric powers of the fundamental representation and their duals. This formula was conjectured by J. van der Jeugt and E. Moens and was generalized the well-known Jacobi-Trudi formula.

Small semisimple subalgebras of semisimple Lie algebras

The main goal of this paper is to prove the following theorem: Let $\frak k$ be an $\frak {sl}_2$-subalgebra of a semisimple Lie algebra $\frak g$, none of whose simple factors is of type $A1$. Then there exists a positive integer $b(\frak k, \frak g)$, such that for every irreducible finite dimensional $\frak g$-module $V$, there exists an injection of $\frak k$-modules $W \to V$, where $W$ is an irreducible $\frak k$-module of dimension less than $b(\frak k, \frak g)$. This result was announced in math.RT/0310140.

On parafermion vertex algebras of $\frak{sl}(2)_{-3/2}$ and $\frak{sl}(3)_{-3/2}$

We study parafermion vertex algebras $N_{-3/2}(\frak{sl}(2))$ and $N_{-3/2}(\frak{sl}(3))$. Using the isomorphism between $N_{-3/2}(\frak{sl}(3))$ and the logarithmic vertex algebra $\mathcal{W}^{0} (2)_{A_2} $ from [2], we show that these parafermion vertex algebras are infinite direct sums of irreducible modules for the Zamolodchikov algebra $\mathcal{W}(2,3)$ of central charge $c=-10$, and that $N_{-3/2}(\frak{sl}(3))$ is a direct sum of irreducible $N_{-3/2}(\frak{sl}(2))$-modules. As a byproduct, we prove certain conjectures about the vertex algebra $\mathcal{W}^0(p)_{A_2}$. We also obtai…

On characters of $L_{\frak{sl}_n}(-Λ_0)$-modules

We use recent results of Rolen, Zwegers, and the first author to study characters of irreducible (highest weight) modules for the vertex operator algebra $L_{\frak{sl}_\ell}(-Λ_0)$. We establish asymptotic behaviors of characters for the (ordinary) irreducible $L_{\frak{sl}_\ell}(-Λ_0)$-modules. As a consequence we prove that their quantum dimensions are one, as predicted by representation theory. We also establish a full asymptotic expansion of irreducible characters for $\frak{sl}_3$. Finally, we determine a decomposition formula for the full characters in terms of unary theta and false thet…

Representations and fusion rules for the orbifold vertex operator algebras $L_{\widehat{\frak{sl}_2}}(k,0)^{\mathbb{Z}_3}$

For the cyclic group $\mathbb{Z}_3$ and positive integer $k$, we study the representations of the orbifold vertex operator algebra $L_{\widehat{\mathfrak{sl}_2}}(k,0)^{\mathbb{Z}_3}$. All the irreducible modules for $L_{\widehat{\mathfrak{sl}_2}}(k,0)^{\mathbb{Z}_3}$ are classified and constructed explicitly. Quantum dimensions and fusion rules for the orbifold vertex operator algebra $L_{\widehat{\mathfrak{sl}_2}}(k,0)^{\mathbb{Z}_3}$ are completely determined.

Classification of finite irreducible conformal modules over $N=2$ Lie conformal superalgebras of Block type

We introduce the $N=2$ Lie conformal superalgebras ${\frak {K}}(p)$ of Block type, and classify their finite irreducible conformal modules for any nonzero parameter $p$. where $p$ is a nonzero complex number. In particular, we show that such a conformal module admits a nontrivial extension of a finite conformal module $M$ over $K_2$ if $p=-1$ and $M$ has rank $(2+2)$, where $K_2$ is an $N=2$ conformal subalgebra of ${\frak {K}}(p)$. As a byproduct, we obtain the classification of finite irreducible conformal modules over a series of finite Lie conformal superalgebras ${\frak k}(n)$ for $n\ge1$…

Integrable highest weight modules over affine superalgebras and number theory

In the first part of the paper we give the denominator identity for all simple finite-dimensional Lie super algebras $\frak g\/$ with a non-degenerate invariant bilinear form. We give also a character and (super) dimension formulas for all finite-dimensional irreducible $\frak g\/$-modules of atypicality $\leq 1\/$ . In the second part of the paper we give the denominator identity for the affine superalgebras $\hat{\frak g}\/$ associated to $\frak g\/$. Specializations of this identity give almost all old and many new formulas for the number of representations of an integer as sums of squares …

Some Koszul properties of standard and irreducible modules

Let $G$ be a simple, simply connected algebraic group over an algebraically closed field of positive characteristic $p$. In recent work, the authors have studied a graded analogue of the category of rational $G$-modules. These gradings are not natural but are "forced" on related algebras though filtrations, often obtained from appropriate quantum structures. This paper presents new results on Koszul modules for the graded algebras obtained through this forced grading process. Most of these results require that the Lusztig character formula holds for all restricted $p$-regular weights, but the …

Odd reflections in the Yangian associated with ${\frak gl}(m|n)$

The odd reflections are an effective tool in the Lie superalgebra representation theory, as they relate non-conjugate Borel subalgebras. We introduce analogues of the odd reflections for the Yangian ${\rm Y}({\frak gl}_{m|n})$ and use them to produce a transition rule for the parameters of the highest weight modules corresponding to a change of the parity sequence. This leads to a description of the finite-dimensional irreducible representations of the Yangian associated with an arbitrary parity sequence.

与李超代数 ${\ rak{osp}}(1|2n)$ 相关的 Yangian 的表示

Representations of the Yangians associated with Lie superalgebras ${\frak{osp}}(1|2n)$

本文借助 Drinfeld 多项式并基于 $n=1$ 的已有结果，完成了与李超代数 ${\ rak{osp}}_{1|2n}$ 相关 Yangian 的有限维不可约表示分类。

Representations of the orbifold VOAS $L_{\hat{\frak{sl}_2}}(k,0)^K$ and the commutant VOAS $C_{{L_{\hat{\mathfrak{so}_m}}(1,0)}^{\otimes 3}}({L_{\hat{\mathfrak{so}_m}}(3,0)})$

For the Klein group $K$, $k\in\mathbb{Z}_{\geqslant 1}$ and $m\in\mathbb{Z}_{\geqslant 4}$, we study the representations of the orbifold vertex operator algebra $L_{\hat{\mathfrak{sl}_2}}(k,0)^{K}$ and the commutant vertex operator algebra of $L_{\hat{\mathfrak{so}_m}}(3,0)$ in $L_{\hat{\mathfrak{so}_m}}(1,0)^{\otimes 3}$ which can be realized as the orbifold vertex operator subalgebra $L_{\hat{\mathfrak{sl}_2}}(2m,0)^{K}$ or its extension. All the irreducible modules for $L_{\hat{\mathfrak{sl}_2}}(k,0)^{K}$ and $C_{{L_{\hat{\mathfrak{so}_m}}(1,0)}^{\otimes 3}}({L_{\hat{\mathfrak{so}_m}}(3,0)}…

Note on the cortex of two-step nilpotent Lie algebras

In this paper, we construct an example of a family of $4d$-dimensional two-step nilpotent Lie algebras $(\frak g_d)_{d\geq 2}$ so that the cortex of the dual of each $\frak g_d$ is a projective algebraic set. More precisely, we show that the cortex of each dual $\frak g_d^*$ of $\frak g_d$ is the zero set of a homogeneous polynomial of degree $d$. This example is a generalization of one given in "Irreducible representations of locally compact groups that cannot be Hausdorff separated from the identity representation" by "{\sc M.E.B. Bekka, and E. Kaniuth}".

D(n,m)型超Yangian的表示

Representations of the super-Yangian of type $D(n,m)$

本文研究D(n,m)型超Yangian的有限维不可约表示分类，给出必要条件并猜想其充分性，对线性最高权表示证明猜想，并构造osp(2|2)与gl(1|2)对应Yangian的同构。

Weight multiplicity free representations, $\frak g$-endomorphism algebras, and Dynkin polynomials

$\frak g$-endomorphism algebras form an interesting class of associative algebras related to the adjoint representation of a semisimple Lie algebra $\frak g$. These algebras were recently introduced by A.Kirillov, who used the term `family algebras'. Let $C_λ$ denote the $\frak g$-endomorphism algebra associated with a simple $\frak g$-module $V_λ$. Most of our results concern the case in which $C_λ$ is commutative, i.e., $V_λ$ is a weight multiplicity free $\frak g$-module. It is proved that $C_λ$ is a polynomial algebra if and only if $λ$ is minuscule. We also characterise in general the num…

Quasi-simple modules and Loewy lengths in modular representations of reductive Lie algebras

Let $\frak g$ be a reductive Lie algebra over an algebraically closed field of characteristic $p>0$. In this paper, we study the representations of $\frak g$ with a $p$-character $χ$ of standard Levi form associated with a given subset $I$ of the simple root system $Π$ of $\frak g$. Let $U_χ({\frak g})$ be the reduced enveloping algebra of $\frak g$. A notion "quasi-simple module" (denoted by $\mathcal L_χ(λ)$) is introduced. The properties of such a module turn out to be better than those of the corresponding simple module $\widehat L_χ(λ)$. It enables us to investigate the $U_χ({\frak g})$-m…

有限一般线性群和酉群的Shalika模型

Shalika Models for Finite General Linear and Unitary Groups

本文完全显式分类了有限一般线性群GL_{2n}(F_q)和有限酉群U_{2n}(F_q)中允许Shalika模型的不可约表示，利用Lusztig的Jordan分解建立了重数公式，并联系了辛模型、线性模型和相对Langlands对偶。

A型和C型超Yangian的表示

Representations of the super Yangians of types $A$ and $C$

本文分类了与正交辛李超代数 osp(2|2n) 相关联的超Yangian的有限维不可约表示，并基于Schur–Sergeev对偶给出了 gl(m|n) Yangian多项式求值模的R-矩阵构造。

Crystal graphs for general linear Lie superalgebras and quasi-symmetric functions

We give a new representation theoretic interpretation of the ring of quasi-symmetric functions. This is obtained by showing that the super analogue of the Gessel's fundamental quasi-symmetric function can be realized as the character of an irreducible crystal for the Lie superalgebra $\frak{gl}_{n|n}$ associated to its non-standard Borel subalgebra with a maximal number of odd isotropic simple roots. We also present an algebraic characterization of these super quasi-symmetric functions.

Orthosymplectic Lie superalgebras, Koszul duality, and a complete intersection analogue of the Eagon-Northcott complex

We study the ideal of maximal minors in Littlewood varieties, a class of quadratic complete intersections in spaces of matrices. We give a geometric construction for a large class of modules, including all powers of this ideal, and show that they have a linear free resolution over the complete intersection and that their Koszul dual is an infinite-dimensional irreducible representation of the orthosymplectic Lie superalgebra. We calculate the algebra of cohomology operators acting on this free resolution. We prove analogous results for powers of the ideals of maximal minors in the variety of l…

Lie群 $SO_0(2,m)$ 的具有非零相对李代数上同调的不可约酉表示

Irreducible unitary representations with non-zero relative Lie algebra cohomology of the Lie group $SO_0(2,m)$

本文针对 Lie 群 $SO_0(2,m)$，确定了具有非零 $(\ rak{g},K)$-上同调的不可约酉表示的等价类数量、上同调 Poincaré 多项式，并识别出其中的离散序列表示与全纯离散序列表示。

Representations of the orthosymplectic Yangian

We give a complete description of the finite-dimensional irreducible representations of the Yangian associated with the orthosymplectic Lie superalgebra $\frak{osp}_{1|2}$. The representations are parameterized by monic polynomials in one variable, they are classified in terms of highest weights. We give explicit constructions of a family of elementary modules of the Yangian and show that a wide class of irreducible representations can be produced by taking tensor products of the elementary modules.

$B(n,m)$型超Yangian的表示

Representations of the super-Yangian of type $B(n,m)$

本文研究$B(n,m)$型超Yangian的有限维不可约表示，通过嵌入定理和Yangian型奇反射推导必要条件，提出充分性猜想并在$n=1$、任意$m\geqslant1$时证明。

The colored symmetric and exterior algebras

We study colored generalizations of the symmetric algebra and its Koszul dual, the exterior algebra. The symmetric group $\mathfrak{S}_n$ acts on the multilinear components of these algebras. While $\mathfrak{S}_n$ acts trivially on the multilinear components of the colored symmetric algebra, we use poset topology techniques to understand the representation on its Koszul dual. We introduce an $\mathfrak{S}_n$-poset of weighted subsets that we call the weighted boolean algebra and we prove that the multilinear components of the colored exterior algebra are $\mathfrak{S}_n$-isomorphic to the top…

On the Action of the Symmetric Group on the Cohomology of Groups Related to (Virtual) Braids

In this paper we consider the cohomology of four groups related to the virtual braids of [Kauffman] and [Goussarov-Polyak-Viro], namely the pure and non-pure virtual braid groups (PvB_n and vB_n, respectively), and the pure and non-pure flat braid groups (PfB_n and fB_n, respectively). The cohomologies of PvB_n and PfB_n admit an action of the symmetric group S_n. We give a description of the cohomology modules H^i(PvB_n,Q) and H^i(PfB_n,Q) as sums of S_n-modules induced from certain one-dimensional representations of specific subgroups of S_n. This in particular allows us to conclude that H^i…

Homology of Littlewood complexes

Let V be a symplectic vector space of dimension 2n. Given a partition λwith at most n parts, there is an associated irreducible representation S_{[λ]}(V) of Sp(V). This representation admits a resolution by a natural complex L^λ, which we call the Littlewood complex, whose terms are restrictions of representations of GL(V). When λhas more than n parts, the representation S_{[λ]}(V) is not defined, but the Littlewood complex L^λstill makes sense. The purpose of this paper is to compute its homology. We find that either L^λis acyclic or that it has a unique non-zero homology group, which forms a…