Fabric idempotents and homological dimensions

Boundary Idempotents and $2$-precluster-tilting categories

The homological theory of Auslander-Platzeck-Todorov on idempotent ideals laid much of the groundwork for higher Auslander-Reiten theory, providing the key technical lemmas for both higher Auslander correspondence as well as the construction of higher Nakayama algebras, among other results. Given a finite-dimensional algebra $A$ and idempotent $e$, we expand on a criterion of Jasso-Külshammer in order to determine a correspondence between the $2$-precluster-tilting subcategories of $\mathrm{mod}(A)$ and $\mathrm{mod}(A/\langle e\rangle)$. This is then applied in the context of generalising dim…

Idempotent ideals and the Igusa-Todorov functions

Let $Λ$ be an artin algebra and $\mathfrak{A}$ a two-sided idempotent ideal of $Λ$, that is, $\mathfrak{A}$ is the trace of a projective $Λ$-module $P$ in $Λ$. We consider the categories of finitely generated modules over the associated rings $Λ/\mathfrak{A}, Λ$ and $Γ=\mathrm{End}_Λ(P)^{op}$ and study the relationship between their homological properties via the Igusa-Todorov functions.

Homological dimensions of crossed products

In this paper we consider several homological dimensions of crossed products $A _α ^σ G$, where $A$ is a left Noetherian ring and $G$ is a finite group. We revisit the induction and restriction functors in derived categories, generalizing a few classical results for separable extensions. The global dimension and finitistic dimension of $A ^σ _α G$ are classified: global dimension of $A ^σ _α G$ is either infinity or equal to that of $A$, and finitistic dimension of $A ^σ _α G$ coincides with that of $A$. A criterion for skew group rings to have finite global dimensions is deduced. Under the hy…

构造幂等子环上极小投射分解的一种方法

A method for constructing minimal projective resolutions over idempotent subrings

本文提出在模范畴内构造幂等子环上极小投射分解的方法，并证明当整体维数和投射维数有限时，满足特定条件的简单模自正交，且推广到夹层幂等子环情形。

Silting modules and ring epimorphisms

There are well-known constructions relating ring epimorphisms and tilting modules. The new notion of silting module provides a wider framework for studying this interplay. To every partial silting module we associate a ring epimorphism which we describe explicitly as an idempotent quotient of the endomorphism ring of the Bongartz completion. For hereditary rings, this assignment is used to parametrise homological ring epimorphisms by silting modules. We further show that homological ring epimorphisms of a hereditary ring form a lattice which completes the poset of noncrossing partitions in the…

Finitistic dimensions and piecewise hereditary property of skew group algebras

Let $Λ$ be a finite dimensional algebra and $G$ be a finite group whose elements act on $Λ$ as algebra automorphisms. Under the assumption that $Λ$ has a complete set $E$ of primitive orthogonal idempotents, closed under the action of a Sylow $p$-subgroup $S \leqslant G$. If the action of $S$ on $E$ is free, we show that the skew group algebra $ΛG$ and $Λ$ have the same finitistic dimension, and have the same strong global dimension if the fixed algebra $Λ^S$ is a direct summand of the $Λ^S$-bimodule $Λ$. Using a homological characterization of piecewise hereditary algebras proved by Happel an…