The module structure of the Solomon-Tits algebra of the symmetric group

Modular Lie powers and the Solomon descent algebra

Let $V$ be an $r$-dimensional vector space over an infinite field $F$ of prime characteristic $p$, and let $L_n(V)$ denote the $n$-th homogeneous component of the free Lie algebra on $V$. We study the structure of $L_n(V)$ as a module for the general linear group $GL_r(F)$ when $n=pk$ and $k$ is not divisible by $p$ and where $n \geq r$. Our main result is an explicit 1-1 correspondence, multiplicity-preserving, between the indecomposable direct summands of $L_k(V)$ and the indecomposable direct summands of $L_n(V)$ which are not isomorphic to direct summands of $V^{\otimes n}$. The direct sum…

Algebras whose Tits form accepts a maximal omnipresent root

Let k be an algebraically closed field and A be a finite-dimensional associative basic k-algebra of the form A=kQ/I where Q is a quiver without oriented cycles or double arrows and I is an admissible ideal of kQ. We consider roots of the Tits form q_A, in particular in case q_A is weakly non-negative. We prove that for any maximal omnipresent root v of q_A, there exists an indecomposable A-module X such that v is the dimension vector of X. Moreover, if A is strongly simply connected, the existence of a maximal omnipresent root of q_A implies that A is tame of tilted type.

Homological properties of Orlik-Solomon algebras

The Orlik-Solomon algebra of a matroid can be considered as a quotient ring over the exterior algebra E. At first we study homological properties of E-modules as e.g. complexity, depth and regularity. In particular, we consider modules with linear injective resolutions. We apply our results to Orlik-Solomon algebras of matroids and give formulas for the complexity, depth and regularity of such rings in terms of invariants of the matroid. Moreover, we characterize those matroids whose Orlik-Solomon ideal has a linear projective resolution and compute in these cases the Betti numbers of the idea…

Tits--Kantor--Koecher范畴中的三位美惠女神

The three graces in the Tits--Kantor--Koecher category

该研究在Tits-Kantor-Koecher范畴中探讨李代数、结合代数与交换结合代数三类代数结构，通过分析自由代数的同调性质及生成元生成的李子代数，考察该范畴在多大程度上模拟对称幺半范畴，以验证相关猜想。

Jordan 代数与权模

Jordan algebras and weight modules

本文研究 Jordan 代数相关的 ${\mathfrak{sl}}_2(J)$ 模，引入 Weyl 模并证明自由 Jordan 代数情形下存在，猜想其构成最高权范畴，以解决上同调消失问题。

Annihilators of Ideals of Exterior Algebras

The Orlik-Solomon algebra A of a matroid is isomorphic to the quotient of an exterior algebra E by a defining ideal I. We find an explicit presentation of the annihilator ideal of I or, equivalently, the E-module dual to A. As an application of that we provide a necessary, combinatorial condition for the algebra A to be quadratic. We show that this is stronger than matroid being line-closed thereby resolving (negatively) a conjecture by Falk. We also show that our condition is not sufficient for the quadraticity.