Tilting sheaves in representation theory of algebras.
A class of finite-dimensional algebras whose Auslander-Reiten quivers have starting but not generalized standard components is investigated. For these components the slices whose slice modules are tilting are considered. Moreover, the endomorphism algebras of tilting slice modules are characterized.
Using geometrical methods, Huisgen-Zimmermann showed that if M is a module with simple top, then M has no proper degeneration such that for all t. Given a module M with square-free top and a projective cover P, she showed that if and only if M has no proper degeneration where M/M ≃ N/N. We prove here these results in a more general form, for hom-order instead of degeneration-order, and we prove them algebraically. The results of Huisgen-Zimmermann follow as consequences from our results....
We investigate derived equivalences between subalgebras of some -Auslander-Yoneda algebras from a class of -angles in weakly -angulated categories. The derived equivalences are obtained by transferring subalgebras induced by -angles to endomorphism algebras induced by approximation sequences. Then we extend our constructions in T. Brüstle, S. Y. Pan (2016) to -angle cases. Finally, we give an explicit example to illustrate our result.
Let A be a finite-dimensional algebra over a field k. We discuss the existence of trisections (mod₊ A,mod₀ A,mod₋ A) of the category of finitely generated modules mod A satisfying exactness, standardness, separation and adjustment conditions. Many important classes of algebras admit trisections. We describe a construction of algebras admitting a trisection of their module categories and, in special cases, we describe the structure of the components of the Auslander-Reiten quiver lying in mod₀ A.
Let S be a commutative local ring of characteristic p, which is not a field, S* the multiplicative group of S, W a subgroup of S*, G a finite p-group, and a twisted group ring of the group G and of the ring S with a 2-cocycle λ ∈ Z²(G,S*). Denote by the set of isomorphism classes of indecomposable -modules of S-rank m. We exhibit rings for which there exists a function such that and is an infinite set for every natural n > 1. In special cases contains every natural number m >...
We prove that for any representation-finite algebra A (in fact, finite locally bounded k-category), the universal covering F: Ã → A is either a Galois covering or an almost Galois covering of integral type, and F admits a degeneration to the standard Galois covering F̅: Ã→ Ã/G, where is the fundamental group of . It is shown that the class of almost Galois coverings F: R → R’ of integral type, containing the series of examples from our earlier paper [Bol. Soc. Mat. Mexicana 17 (2011)], behaves...