Radical cube zero weakly symmetric algebras and support varieties

Newton-Okounkov bodies of Bott-Samelson varieties and Grossberg-Karshon twisted cubes

We describe, under certain conditions, the Newton-Okounkov body of a Bott-Samelson variety as a lattice polytope defined by an explicit list of inequalities. The valuation that we use to define the Newton-Okounkov body is different from that used previously in the literature. The polytope that arises is a special case of the Grossberg-Karshon twisted cubes studied by Grossberg and Karshon in connection to character formulae for irreducible $G$-representations and also studied previously by the authors in relation to certain toric varieties associated to Bott-Samelson varieties.

Central ideals and Jacobson radicals of blocks of group algebras

We study the relationship between the central ideals and the Jacobson radicals of blocks of group algebras.In particular, we characterize the blocks with the property that the square of the radical is a non-zero central ideal. Moreover, we also consider the blocks with the property that the cube of the radical becomes a non-zero central ideal.

一类有限维代数表示簇的不可约分量

Irreducible components of varieties of representations of a class of finite dimensional algebras

针对一类三次截断且带额外关系的非交换多项式代数，本文通过证明固定根分层或底座分层子簇的不可约性并比较两类覆盖，确定了其表示簇的不可约分量。

Finitistic dimension through infinite projective dimension

We show that an artin algebra having at most three radical layers of infinite projective dimension has finite finitistic dimension, generalizing the known result for algebras with vanishing radical cube.

Brauer configuration algebras: A generalization of Brauer graph algebras

In this paper we introduce a generalization of a Brauer graph algebra which we call a Brauer configuration algebra. As with Brauer graphs and Brauer graph algebras, to each Brauer configuration, there is an associated Brauer configuration algebra. We show that Brauer configuration algebras are finite dimensional symmetric algebras. After studying and analysing structural properties of Brauer configurations and Brauer configuration algebras, we show that a Brauer configuration algebra is multiserial; that is, its Jacobson radical is a sum of uniserial modules whose pairwise intersection is eith…

Quotient of Deligne-Lusztig varieties

We study the quotient of parabolic Deligne-Lusztig varieties by a finite unipotent group U^F where U is the unipotent radical of a rational parabolic subgroup P = L U. We show that in some particular cases the cohomology of this quotient can be expressed in terms of "smaller" parabolic Deligne-Lusztig varieties associated to the Levi subgroup L.

斜群代数、(Fg) 与自内射根立方零代数

Skew Group Algebras, (Fg) and Self-injective Rad-Cube-Zero Algebras

本文利用斜群代数与可分等价对自内射根立方零代数是否满足 (Fg) 型有限生成条件进行分类，补充并完成了既有部分分类工作。

Problems of classifying associative or Lie algebras and triples of symmetric or skew-symmetric matrices are wild

We prove that the problems of classifying triples of symmetric or skew-symmetric matrices up to congruence, local commutative associative algebras with zero cube radical and square radical of dimension 3, and Lie algebras with central commutator subalgebra of dimension 3 are hopeless since each of them reduces to the problem of classifying pairs of n-by-n matrices up to simultaneous similarity.

Shimura varieties with $Γ_1(p)$-level via Hecke algebra isomorphisms: the Drinfeld case

We study the local factor at p of the semi-simple zeta function of a Shimura variety of Drinfeld type for a level structure given at p by the pro-unipotent radical of an Iwahori subgroup. Our method is an adaptation to this case of the Langlands-Kottwitz counting method. We use Hecke algebra isomorphisms to determine the test functions at p.

Elementary Subalgebrs of Lie Algebras

We initiate the investigation of the projective varieties $\mathbb E(r,\mathfrak g)$ of elementary subalgebras of dimension $r$ of a ($p$-restricted) Lie algebra $\mathfrak g$ for various $r \geq 1$. These varieties $\mathbb E(r,\mathfrak g)$ are the natural ambient varieties for generalized support varieties for restricted representations of $\mathfrak g$. We identify these varieties in special cases, revealing their interesting and varied geometric structures. We also introduce invariants for a finite dimensional $\mathfrak u(\mathfrak g)$-module $M$, the local $(r,j)$-radical rank and local…

Multiserial and special multiserial algebras and their representations

In this paper we study multiserial and special multiserial algebras. These algebras are a natural generalization of biserial and special biserial algebras to algebras of wild representation type. We define a module to be multiserial if its radical is the sum of uniserial modules whose pairwise intersection is either 0 or a simple module. We show that all finitely generated modules over a special multiserial algebra are multiserial. In particular, this implies that, in analogy to special biserial algebras being biserial, special multiserial algebras are multiserial. We then show that the class …

Representation varieties of algebras with nodes

We study the behavior of representation varieties of quivers with relations under the operation of node splitting. We show how splitting a node gives a correspondence between certain closed subvarieties of representation varieties for different algebras, which preserves properties like normality or having rational singularities. Furthermore, we describe how the defining equations of such closed subvarieties change under the correspondence. By working in the "relative setting" (splitting one node at a time), we demonstrate that there are many non-hereditary algebras whose irreducible components…

约化李代数的可区分模的湮没簇

Annihilator varieties of distinguished modules of reductive Lie algebras

本文研究实约化群可区分表示的微局域必要条件，推广Vogan定理，应用于分支问题、混合模型及局部theta对应，并验证Prasad猜想。