RTAA

Representation Theory of Algebras and Applications

Fridays at 16:00 ( Zoom)

Organizers: Kostiantyn Iusenko, John MacQuarrie and Eduardo Marcos.

Seminar Mailing List: RTAA — Representações das Álgebras e Aplicações

FORTHCOMING WEBINARS

22 October, 2021	Valente Santiago Universidad Nacional Autónoma de México Triangular matriz categories and recollements We define the analogous of the triangular matrix algebra to the context of rings with several objects. Given two additive categories $\mathcal{U}$ and $\mathcal{T}$ and $M \in$ $\operatorname{Mod}\left(\mathcal{U} \otimes \mathcal{T}^{o p}\right)$ we will construct the triangular matrix category $\boldsymbol{\Lambda}:=\left[\begin{array}{ll}\mathcal{T} & 0 \\ M & \mathcal{U} \end{array}\right]$ and we prove that there is an equivalence $(\operatorname{Mod}(\mathcal{T}), \mathbb{G M o d}(\mathcal{U})) \simeq \operatorname{Mod}(\boldsymbol{\Lambda})$. We will show that if $\mathcal{U}$ and $\mathcal{T}$ are dualizing $K$-varieties and $M \in \operatorname{Mod}\left(\mathcal{U} \otimes \mathcal{T}^{o p}\right)$ satisfies certain conditions then $\boldsymbol{\Lambda}:=\left[\begin{array}{ll}\mathcal{T} & 0 \\ M& \mathcal{U}\end{array}\right]$ is a dualizing variety. Finally, we will show that given a recollement between functor categories we can induce a new recollement between triangular matrix categories, this is a generalization of a result given by Chen and Zheng in [Q. Chen, M. Zheng. Recollements of abelian categories and special types of comma categories. J. Algebra. 321 (9), 2474-2485 (2009), Theorem 4.4].
29 October, 2021	Luis Gabriel Rodríguez Valdés Universidad Nacional Autónoma de México TBA TBA
05 November, 2021	Hipolito Treffinger Universität Bonn TBA TBA
12 November, 2021	Marco A. Pérez Instituto de Matemática y Estadística "Prof. Ing. Rafael Laguardia" TBA TBA
19 November, 2021	Alex Sierra Cárdenas Universidade Federal do Pará On Brauer configurations induced by finite groups Aspects of the representation theory of a Brauer configuration algebra, such as the Cartan matrix and the module length of the respective indecomposable modules, have shown the existence of combinatorial relations that are satisfied by any finite group. The aim of this talk is to present both the Cartan matrix of a Brauer configuration algebra and the module length of any indecomposable projective module associated to a Brauer configuration algebra. Then using these aspects and the concept of subgroup-occurrence of an element in a group, we demonstrate a couple of combinatorial relations satisfied by any finite group, when considering the Brauer configuration induced by a finite group of an order different from a prime number.
26 November, 2021	Rosanna Laking Università degli Studi di Verona TBA TBA
03 December, 2021	Mark Kleiner Syracuse University TBA TBA

PAST WEBINARS

15 October, 2021	Oliver Lorscheid University of Groningen Representation type via quiver Grassmannians The representation type of a quiver $Q$ can be characterized by the geometric properties of the associated quiver Grassmannians: (a) $Q$ is representation finite iff. all quiver Grassmannians are smooth and have cell decompositions into affine spaces; (b) $Q$ is tame iff. all quiver Grassmannians have cell decompositions into affine spaces and if there exist singular quiver Grassmannians; (c) $Q$ is wild iff. every projective variety occurs as a quiver Grassmannian. With the exception of (extended) Dynkin type $E$, this result is proven in joint work with Thorsten Weist. The missing parts for Type $E$ were completed by Cerulli Irelli-Esposito-Franzen-Reineke. In this talk, we will explain this result and parts of its proof. Show abstract
08 October, 2021	Jeremy Rickard University of Bristol Generation of the unbounded derived category of a ring If $R$ is a ring, recall that the derived category $D(R)$ is a category whose objects are chain complexes of $R$-modules. In recent decades, $D(R)$ has been recognized to be of great importance in studying the homological algebra of R. There are several ways in which a class of objects might be said to “generate” $D(R)$. For example, it is an exercise to show that the projective $R$-modules generate $D(R)$ as a triangulated category with coproducts (or that the injective modules do if we use products in place of coproducts). It seems more unnatural to ask whether the injective modules generate $D(R)$ as a triangulated category with coproducts, but we will discuss how this question is related to well-known open questions such as the Finitistic Dimension Conjecture. Show abstract
01 October, 2021	Robinson-Julian Serna UPTC, Colombia A link between representations of peak posets and cluster algebras In this talk, we show a link between the theory of cluster algebras and the theory of representations of posets. Particularly, we give a geometric interpretation of the category of finitely generated socle-projective representations over the incidence algebra of a poset of type $A$ as a combinatorial category of certain diagonals of a regular polygon. This construction is inspired by the realization of the cluster category of type $A$ as the category of all diagonals by Caldero-Chapoton-Schiffler. Moreover, given a poset $P$ of type $A$, we define a subalgebra $B(P)$ of a cluster algebra $B$ and we establish a sufficient condition to conclude $B=B(P)$. This is a joint work with R. Schiffler. Show abstract
24 September, 2021	Fernando dos Reis Naves UFMG Um relacionamento funtorial entre álgebras e seus quocientes pelas $n$-ésimas potências do radical de Jacobson A famosa construção de Gabriel provou que uma álgebra de dimensão finita pode ser vista como um quociente de uma álgebra de caminhos por um ideal admissível. A construção permitiu olhar para teoria de representação de álgebras de dimensão finita de um modo combinatório. Iusenko, MacQuarrie e Quirino exibiram uma adjunção que explica de maneira muito precisa a filosofia da construção de Gabriel. A adjunção deles é obtida utilizando uma relação de equivalência nos morfismos das álgebras. Nesta palestra, mostraremos que a construção de Gabriel pode ser obtida utilizando uma relação mais fina. Além disso, através de uma adjunção, provaremos que há uma classe de álgebras que podem ser aproximadas por álgebras quadráticas, isto é, um quociente de uma álgebra de caminhos por um ideal homogêneo de grau 2. Show abstract
17 September, 2021	Andrea Solotar Universidad de Buenos Aires Invariants of gentle algebras Gentle and locally gentle algebras are quadratic Koszul algebras. The isomorphism classes of gentle algebras are in bijection with dissections of certain types of surfaces. Homological methods provide important information about this family of algebras. The invariants obtained in this way are in fact derived invariants. In this talk I will describe derived invariants -some of them already known and some of them new- of gentle algebras obtained via their Hochschild cohomology and homology, taking all the structure into account: the homology and cohomology vector spaces, the cohomology graded commutative algebra, the Gerstenhaber bracket and the cap product. This is a joint work with Cristian Chaparro Acosta, Sibylle Schroll and Mariano Suárez-Álvarez. Show abstract
10 September, 2021	Claudiano Henrique da Cunha Melo UFMG Álgebras seriais sem ciclos truncadas são derivadamente equivalentes a álgebras de incidência de posets Dada uma álgebra serial sem ciclos truncada $\Lambda$, denotamos sua categoria derivada por $\mathcal{D}^b(\Lambda).$ Nesta palestra apresentaremos a construção de um complexo inclinante $T_{\Lambda}$ e definiremos um conjunto parcialmente ordenado $S_{\Lambda}$ tais que a álgebra de endomorfismos $End_{\mathcal{D}^b(\Lambda)} T_{\Lambda}$ é isomorfa à álgebra de incidência de poset $kS_{\Lambda}^{op}$. Com isso, usando o Teorema de Rickard podemos concluir que $\Lambda$ é derivadamente equivalente a $kS_{\Lambda}^{op}$. Show abstract
03 September, 2021	Edson Ribeiro Alvares Universidade Federal do Paraná Ação do grupo de tranças em sequências excepcionais e aplicações para álgebras hereditárias por partes Nesta palestra, vamos introduzir o conceito de mutação de sequências excepcionais em categorias de feixes coerentes. Estas mutações permitem definir a ação do grupo de tranças sobre sequências excepcionais. Com o uso eficiente do Teorema de Riemann-Roch e a Teoria de Auslander-Reiten, podemos tirar bons resultados sobre as órbitas desta ação. Estes resultados nos trazem um melhor entendimento sobre as álgebras que são derivadamente equivalente a categoria de feixes coerentes sobre retas projetivas com peso. Show abstract
30 July, 2021	Gustavo Mata Universidad de la República, Uruguay Topics on the Igusa-Todorov functions One of the most important conjecture in the representation theory of Artin algebras is the finitistic dimension conjecture. It states that $sup\{pd(M) : M\ \text{is a f.g module of finite projective dimension}\}$ is finite. In an attempt to prove the conjecture this conjecture Igusa and Todorov defined in “On finitistic global dimension conjecture for artin algebras”, two functions from the objects of modA to the natural numbers, which generalize the notion of projective dimension. Nowadays they are known as the Igusa-Todorov functions. In this talk I will introduce the Igusa-Todorov functions and their main properties. We will also see how to use these functions to prove the finitistic dimension conjecture in several contexts. Show abstract
23 July, 2021	Danilo Dias da Silva Universidade Federal de Sergipe Feixes instantons e representações de aljavas O seminário terá como tema apresentar uma nova compactificação para o espaço de módulos (moduli spaces) de feixes intantons de carga $1$ sobre $\mathbb P^3$. Isto será feito identificando estes feixes com representações de uma aljava com três vértices e oito flechas que atendem certas propriedades e olhando essas representações no espaço de módulos de King de representações teta-estáveis sobre esta aljava. Show abstract
16 July, 2021	Mariano Suárez-Álvarez Universidad de Buenos Aires On the modular automorphism of twisted Calabi-Yau algebras A twisted Calabi-Yau algebra $A$ is, by definition, endowed with an automorphism $\sigma:A\to A$, well-defined only up to inner automorphisms, that controls the duality theory for representations of $A$. The algebra is Calabi-Yau, and not only twistedly so, precisely when $\sigma$ can be taken to be inner and even the identity map of $A$, but in general it cannot. The objective of the talk will be to present some results that give information about this automorphism in the general situation, and show how it can be used to construct interesting and non-trivial invariants of the algebra, of automorphisms and derivations of the algebra, and of related objects. Some applications of these invariants to the problem of computing Hochschild cohomology and the automorphism groups of our algebras will be discussed. Show abstract
25 June, 2021	Eduardo Marcos IME-USP Variety defined by the Groebner basis of a module This is a joint project with Ed. Green and Schroll Sibylle. Our set up is an algebra of the form $kQ/I$, ($I$ is admissible, for simplification). Given a right module M we define, using its right groebner basis, a variety. Each point in this variety corresponds to a module which has the same tip set. Each module corresponding to a point in the variety has the same dimension vector of the original module. We denote this variety by $V(M)$. There is a natural injection of sets $V(M) \to V_d(KQ)$, where $V_d(kQ)$ is the usual variety of representations Q representations of dimension vector $d$. We do not know if the injection is a morphism of varieties ( I conjecture it is). We also do not know which subgroup of $Gl_d$ let the subset of the variety be invariant, so we would have a grupo acting on it. Some curious results, for instance, is that if the module is an indecomposable projective then our variety consists of one point. I am open to suggestions etc... Show abstract
18 June, 2021	Ricardo Franquiz UFMG Álgebra de Árvore de Brauer e Blocos de Grupos Profinitos Sejam $G$ um grupo profinito , $k$ um corpo de característica $p> 0$. A álgebra de grupo completa de G, $k[[G]]$, possui uma decomposição como um produto direto de álgebras pseudocompactas indecomponíveis, que chamaremos de blocos. Cada bloco de $k[[G]]$ tem associado um pro-$p$ subgrupo de $G$ chamado grupo de defeito. O grupo de defeito proporciona uma medida que tão próximo estará um bloco de ser uma álgebra semisimples. Nesta palestra explicaremos como associar a cada bloco um grupo de defeito e descreveremos os blocos cujo grupo de defeito é um grupo cíclico usando a estrutura de álgebra de árvore de Brauer. Este trabalho foi feito junto com o John Macquarrie. Show abstract
11 June, 2021	Joseph Grant University of East Anglia Preprojective algebras: classical and higher I will give an introduction to representations of quivers, aimed at non-experts, and then introduce preprojective algebras of quivers. Iyama showed how many nice aspects of the representations of quivers generalise to certain algebras of higher global dimension, and the preprojective algebra can be defined in this setting. I will explain some results on higher preprojective algebras obtained in joint work with Osamu Iyama. Show abstract
04 June, 2021	Valeriano Lanza UFF Moduli of flags of sheaves: a quiver description In [1], the moduli spaces of framed flags of sheaves on $\mathbb P^2$ were described by means of representations of the so-called enhanced ADHM quiver. We first review those results, with a recent refinement concerning the chamber structure in the space of stability parameters. We shall then discuss the obstruction theory for these moduli spaces, showing in general that they have a perfect obstruction theory, and providing for specific choices of invariants a class of unobstructed points. Finally, open problems and possible further developments will be presented. This is a joint work with Rodrigo von Flach and Marcos Jardim. 1. R. A. von Flach and M. Jardim, Moduli spaces of framed flags of sheaves on the projective plane. Journal of Geometry and Physics 118 (2017), 138–168. Show abstract
14 May, 2021	Vitor Gulisz UFPR Higher Auslander-Reiten theory: what is it and how to understand it Higher Auslander-Reiten theory was introduced by Osamu Iyama in the 2000s as a generalization of the theory developed by Maurice Auslander and Idun Reiten in the 1970s. In this talk, we will discuss what is this theory and how to understand it. In doing so, we will examine both the definitions of $n$-almost split sequence and of $n$-cluster tilting subcategory. In the end, we will also look at some open problems of the theory. Show abstract
07 May, 2021	John MacQuarrie UFMG Propriedades homológicas de álgebras preservadas por certas extensões Uma extensão de álgebras associativas é simplesmente uma álgebra associativa $A$ com subálgebra $B$. Em uma sequência de artigos recentes, Cibils, Lanzilotta, Marcos e Solotar colocaram condições sobre a extensão (extensões "limitadas") e mostraram que, sobre essas condições, duas propriedades homológicas valem para $B$ se, e somente se, valem para $A$: nomeadamente "dimensão global finita" e "suporte da homologia de Hochschild finita". Em particular, segue disso que a "Conjectura de Han" vale para $B$ se, e somente se, vale para $A$. Kostiantyn Iusenko e eu temos interesse numa classe de álgebras que generaliza naturalmente a classe de álgebras de dimensão finita: as Álgebras Pseudocompactas. Para estender os resultados de CLMS, a gente generalizou as condições de "extensões limitadas" e provou que as propriedades nomeadas acima continuam sendo preservadas por nossa classe mais geral de extensões. Explicarei todas as palavras desse resumo e darei umas das ideias da generalização. Show abstract