arXiv subjects
Publications and source records attributed to Crystal Hoyt.
We review old and new results concerning the $DS$ functor and associated varieties for Lie superalgebras. These notions were introduced in the unpublished manuscript arXiv:math/0507198 by Michel Duflo and the third author. This paper includes the results and proofs of the original manuscript, as well as a survey of more recent results.
The Lie superalgebra $W(\infty)$ is defined to be the direct limit of the simple finite-dimensional Cartan type Lie superalgebras $W(n)$ as $n$ goes to infinity, where $W(n)$ denotes the Lie superalgebra of superderivations of the Grassmann algebra $Λ(n)$. The zeroth component of $W(\infty)$ in its natural $\mathbb{Z}$-grading is isomorphic to $\mathfrak{gl}(\infty)$. In this paper, we initiate the study of the representation theory of $W(\infty)$. We study $\mathbb{Z}$-graded $W(\infty)$-modules, and we introduce a category $\mathbb{T}_W$ that is closely related to the Koszul category $\mathbb{T}_{\mathfrak{sl}(\infty)}$ of tensor $\mathfrak{sl}(\infty)$-modules introduced and studied by Dan-Cohen, Serganova and Penkov. We classify the simple objects of $\mathbb{T}_W$ (up to isomorphism). We prove that each simple module in $\mathbb{T}_W$ is isomorphic to the unique simple quotient of a module induced from a simple module in $\mathbb{T}_{\mathfrak{gl}(\infty)}$, and vice versa, which is analogous to the case for $W(n)$ studied by Serganova. As a corollary, we find that all simple modules in $\mathbb{T}_W$ are highest weight modules with respect to a certain Borel subalgebra. We realize each simple module from $\mathbb{T}_W$ as a module of tensor fields, generalizing work of Bernstein and Leites for $W(n)$. We prove that the category $\mathbb{T}_W$ has enough injective objects, and for each simple module, we provide an explicit injective module in $\mathbb{T}_W$ that contains it.
We prove denominator identities for the periplectic Lie superalgebra $\mathfrak{p}(n)$, thereby completing the problem of finding denominator identities for all simple classical finite-dimensional Lie superalgebras.
We introduce and study new categories T(g,k)of integrable sl(\infty)-modules which depend on the choice of a certain reductive subalgebra k in g=sl(\infty). The simple objects of these categories are tensor modules as in the previously studied category, however, the choice of k provides more flexibility of nonsimple modules. We then choose k to have two infinite-dimensional diagonal blocks, and show that a certain injective object K(m|n) in T(g,k) realizes a categorical sl(\infty)-action on the integral category O(m|n) of the Lie superalgebra gl(m|n). We show that the socle of K(m|n) is generated by the projective modules in O(m|n), and compute the socle filtration of K(m|n) explicitly. We conjecture that the socle filtration of K(m|n) reflects a "degree of atypicality filtration" on the category O(m|n). We also conjecture that a natural tensor filtration on K(m|n) arises via the Duflo--Serganova functor sending the category O(m|n) to O(m-1|n-1). We prove this latter conjecture for a direct summand of K(m|n) corresponding to the finite-dimensional gl(m|n)-modules.
We show that the Duflo-Serganova functor on the category of finite-dimensional modules over a finite-dimensional contragredient Lie superalgebra induces a ring homomorphism on a natural quotient of the Grothendieck ring, which is isomorphic to the ring of characters. We realize this homomorphism as a certain evaluation of functions related to the supersymmetry property. We use this realization to describe the kernel and image of the homomorphism induced by the Duflo-Serganova functor.
In 1994, Kac and Wakimoto suggested a generalization of Bernstein and Leites character formula for basic Lie superalgebras, and the natural question was raised: to which simple highest weight modules does it apply? In this paper, we prove a similar formula for a large class of finite-dimensional simple modules over the Lie superalgebra gl(m|n), which we call piecewise disconnected modules, or PDC. The class of PDC modules naturally includes totally connected modules and totally disconnected modules, the two families for which similiar character formulas were proven by Su and Zhang as special cases of their general formula. This paper is part of our program for the pursuit of elegant character formulas for Lie superalgebras.
A contragredient Lie superalgebra is a superalgebra defined by a Cartan matrix. In general, a contragredient Lie superalgebra is not finite dimensional, however it has a natural Z-grading by finite dimensional components. A contragredient Lie superalgebra has finite growth if the dimensions of these graded components depend polynomially on the degree. We discuss the classification of finite-growth contragredient Lie superalgebras. (Joint work with Vera Serganova)
We discuss the classification of good Z-gradings of basic Lie superalgebras. This problem arose in connection to W-algebras, where good Z-gradings play a role in their construction.
A weight module of a basic Lie superalgebra is called finite if all of its weight spaces are finite dimensional, and it is called bounded if there is a uniform bound on the dimension of a weight space. The minimum bound is called the degree of the module. For the basic Lie superalgebra D(2,1,a), we prove that every simple weight module is bounded and has degree less than or equal to 8. This bound is attained by a cuspidal module if and only if it is "typical". Atypical cuspidal modules have degree less than or equal to 6 and greater than or equal to 2.
Character formulas for Lie superalgebras have been shown to have important applications to number theory and combinatorics. We prove the Kac-Wakimoto character formula for the general linear Lie superalgebra gl(m|n). This formula specializes to the well-known Kac-Weyl character formula when the modules are typical and to the Weyl denominator identity when the module is trivial. We also prove a determinantal character formula for KW-modules using the Kac-Wakimoto character formula.
We classify good Z-gradings of basic Lie superalgebras over an algebraically closed field of characteristic zero. Good Z-gradings are used in quantum Hamiltonian reduction for affine Lie superalgebras, where they play a role in the construction of super W-algebras. We also describe the centralizer of a nilpotent even element and of an sl(2)-triple in gl(m|n) and osp(m|2n).
We define regular Kac-Moody superalgebras and classify them using integrable modules. We give conditions for irreducible highest weight modules of regular Kac-Moody superalgebras to be integrable. This paper is a major part of the proof for the classification of finite-growth contragredient Lie superalgebras.
A contragredient Lie superalgebra is a superalgebra defined by a Cartan matrix. A contragredient Lie superalgebra has finite-growth if the dimensions of the graded components (in the natural grading) depend polynomially on the degree. In this paper we classify finite-growth contragredient Lie superalgebras. Previously, such a classification was known only for the symmetrizable case.
We prove an explicit condition on the level $k$ for the irreducibility of a vacuum module $V^{k}$ over a (non-twisted) affine Lie superalgebra, which was conjectured by M. Gorelik and V.G. Kac. An immediate consequence of this work is the simplicity conditions for the corresponding minimal W-algebras obtained via quantum reduction, in all cases except when the level $k$ is a non-negative integer.