scholarly journals Combinatorics of Exceptional Sequences in Type A

10.37236/6251 ◽  
2019 ◽  
Vol 26 (1) ◽  
Author(s):  
Alexander Garver ◽  
Kiyoshi Igusa ◽  
Jacob P. Matherne ◽  
Jonah Ostroff
Keyword(s):  
Dynkin Diagram ◽  
Type A ◽  
Linear Extensions ◽  
Quiver Representations ◽  
Noncrossing Partitions ◽  
Underlying Graph ◽  
Exceptional Sequences

Exceptional sequences are certain sequences of quiver representations.  We introduce a class of objects called strand diagrams and use these to classify exceptional sequences of representations of a quiver whose underlying graph is a type $\mathbb{A}_n$ Dynkin diagram. We also use variations of these objects to classify $c$-matrices of such quivers, to interpret exceptional sequences as linear extensions of explicitly constructed posets, and to give a simple bijection between exceptional sequences and certain saturated chains in the lattice of noncrossing partitions. 

scholarly journals A combinatorial model for exceptional sequences in type A

2015 ◽  
Vol DMTCS Proceedings, 27th... (Proceedings) ◽  
Author(s):  
Alexander Garver ◽  
Jacob P. Matherne
Keyword(s):  
Type A ◽  
Linear Extensions ◽  
Quiver Representations ◽  
Noncrossing Partitions ◽  
Labeled Trees ◽  
Combinatorial Model ◽  
International Audience ◽  
Exceptional Sequences ◽  
Nous Utilisons

International audience Exceptional sequences are certain ordered sequences of quiver representations. We use noncrossing edge-labeled trees in a disk with boundary vertices (expanding on T. Araya’s work) to classify exceptional sequences of representations of $Q$, the linearly ordered quiver with $n$ vertices. We also show how to use variations of this model to classify $c$-matrices of $Q$, to interpret exceptional sequences as linear extensions, and to give a simple bijection between exceptional sequences and certain chains in the lattice of noncrossing partitions. In the case of $c$-matrices, we also give an interpretation of $c$-matrix mutation in terms of our noncrossing trees with directed edges. Les suites exceptionnelles sont certaines suites ordonnées de représentations de carquois. Nous utilisons des arbres aux arêtes étiquetés et aux sommets dans le bord d’un disque (expansion sur le travail de T. Araya) pour classifier les suites exceptionnelles de représentations du carquois linéairement ordonné à $n$ sommets. Nous exploitons des variations de ce modèle pour classifier les $c$-matrices dudit carquois, pour interpréter les suites exceptionnelles comme des extensions linéaires, et pour donner une bijection élémentaire entre les suites exceptionnelles et certaines chaînes dans le réseau des partitions sans croisement. Dans le cas des $c$-matrices, nous donnons également une interprétation de la mutation des $c$-matrices en termes des arbres sans croisement aux arêtes orientés.

scholarly journals On Generalized Minors and Quiver Representations

2018 ◽  
Vol 2020 (3) ◽  
pp. 914-956 ◽  
Author(s):  
Dylan Rupel ◽  
Salvatore Stella ◽  
Harold Williams
Keyword(s):  
Finite Type ◽  
Dynkin Diagram ◽  
Cluster Algebra ◽  
Coordinate Ring ◽  
Coxeter Element ◽  
Quiver Representations ◽  
Group Representations ◽  
Weight Group ◽  
Highest Weight ◽  
Bruhat Cell

Abstract The cluster algebra of any acyclic quiver can be realized as the coordinate ring of a subvariety of a Kac–Moody group—the quiver is an orientation of its Dynkin diagram, defining a Coxeter element and thereby a double Bruhat cell. We use this realization to connect representations of the quiver with those of the group. We show that cluster variables of preprojective (resp. postinjective) quiver representations are realized by generalized minors of highest-weight (resp. lowest-weight) group representations, generalizing results of Yang–Zelevinsky in finite type. In type $A_{n}^{\!(1)}$ and finitely many other affine types, we show that cluster variables of regular quiver representations are realized by generalized minors of group representations that are neither highest- nor lowest-weight; we conjecture this holds more generally.

scholarly journals From m-clusters to m-noncrossing partitions via exceptional sequences

2011 ◽  
Vol 271 (3-4) ◽  
pp. 1117-1139 ◽  
Author(s):  
Aslak Bakke Buan ◽  
Idun Reiten ◽  
Hugh Thomas
Keyword(s):  
Noncrossing Partitions ◽  
Exceptional Sequences

scholarly journals $m$-noncrossing partitions and $m$-clusters

2009 ◽  
Vol DMTCS Proceedings vol. AK,... (Proceedings) ◽  
Author(s):  
Aslak Bakke Buan ◽  
Idun Reiten ◽  
Hugh Thomas
Keyword(s):  
Positive Integer ◽  
Root System ◽  
Cluster Algebra ◽  
Reflection Group ◽  
Catalan Number ◽  
Explicit Description ◽  
Noncrossing Partitions ◽  
Il Y A ◽  
International Audience ◽  
Exceptional Sequences

International audience Let $W$ be a finite crystallographic reflection group, with root system $\Phi$. Associated to $W$ there is a positive integer, the generalized Catalan number, which counts the clusters in the associated cluster algebra, the noncrossing partitions for $W$, and several other interesting sets. Bijections have been found between the clusters and the noncrossing partitions by Reading and Athanasiadis et al. There is a further generalization of the generalized Catalan number, sometimes called the Fuss-Catalan number for $W$, which we will denote $C_m(W)$. Here $m$ is a positive integer, and $C_1(W)$ is the usual generalized Catalan number. $C_m(W)$ counts the $m$-noncrossing partitions for $W$ and the $m$-clusters for $\Phi$. In this abstract, we will give an explicit description of a bijection between these two sets. The proof depends on a representation-theoretic reinterpretation of the problem, in terms of exceptional sequences of representations of quivers. Soit $W$ un groupe de réflexions fini et cristallographique, avec système de racines $\Phi$. Associé à $W$, il y a un entier positif, le nombre de Catalan généralisé, qui compte les amas dans l'algèbre amassée associée, les partitions non-croisées de $W$, et plusieurs autres ensembles intéressantes. Des bijections entre les amas et les partitions non-croisées ont été données par Reading et Athanasiadis et al. On peut encore généraliser le nombre de Catalan généralisé, obtenant le nombre Fuss-Catalan de $W$, que nous noterons $C_m(W)$. Ici $m$ est un entier positif, et $C_1(W)$ est le nombre Catalan généralisé standard. $C_m(W)$ compte les partitions $m$-non-croisées de $W$ et les $m$-amas de $\Phi$. Dans ce résumé, nous donnerons une bijection explicite entre ces deux ensembles. La démonstration dépend d'une réinterprétation des objets du point de vue des suites exceptionnelles de représentations de carquois.

THE RESTRICTIONS OF REPRESENTATIONS OF ALGEBRAIC GROUPS OF TYPES Bn AND Dn TO SUBGROUPS OF TYPE A2

2005 ◽  
Vol 04 (05) ◽  
pp. 467-479 ◽  
Author(s):  
ANNA A. OSINOVSKAYA
Keyword(s):  
Dynkin Diagram ◽  
Algebraic Groups ◽  
Type A ◽  
Composition Factors

Restrictions of modular p-restricted representations of algebraic groups of types Bn (n > 2) and Dn (n > 3) to naturally embedded subgroups of type A2 are studied. The composition factors of such restrictions are determined in the case of locally small highest weights. Here the class of locally small weights depends upon the type of a group considered and is defined in terms of their values on four simple roots linked at the Dynkin diagram of a group.

scholarly journals Tilting modules and exceptional sequences for leaf quotients of type A zig-zag algebras

2019 ◽  
Vol 61 (2) ◽  
pp. 189-207
Author(s):  
Elin Persson Westin
Keyword(s):  
Type A ◽  
Tilting Modules ◽  
Related Family ◽  
The Family ◽  
Hereditary Algebras ◽  
Exceptional Sequences ◽  
Generalized Tilting Modules

Abstract We classify generalized tilting modules and full exceptional sequences for the family of quasi-hereditary quotients of type A zig-zag algebras and for a related family of algebras. We also give a characterization of these quotients as quasi-hereditary algebras with simple preserving duality that are “close” to self-injective algebras.

scholarly journals Noncrossing partitions and representations of quivers

2009 ◽  
Vol 145 (6) ◽  
pp. 1533-1562 ◽  
Author(s):  
Colin Ingalls ◽  
Hugh Thomas
Keyword(s):  
Coxeter Group ◽  
Stability Condition ◽  
Quiver Representations ◽  
Finitely Generated ◽  
Cluster Category ◽  
Noncrossing Partitions ◽  
Finite Coxeter Group ◽  
Group Form ◽  
Cluster Tilting ◽  
Tilting Objects

AbstractWe situate the noncrossing partitions associated with a finite Coxeter group within the context of the representation theory of quivers. We describe Reading’s bijection between noncrossing partitions and clusters in this context, and show that it extends to the extended Dynkin case. Our setup also yields a new proof that the noncrossing partitions associated with a finite Coxeter group form a lattice. We also prove some new results within the theory of quiver representations. We show that the finitely generated, exact abelian, and extension-closed subcategories of the representations of a quiver Q without oriented cycles are in natural bijection with the cluster tilting objects in the associated cluster category. We also show that these subcategories are exactly the finitely generated categories that can be obtained as the semistable objects with respect to some stability condition.

scholarly journals Stable rigged configurations and Littlewood―Richardson tableaux

2011 ◽  
Vol DMTCS Proceedings vol. AO,... (Proceedings) ◽  
Author(s):  
Masato Okado ◽  
Reiho Sakamoto
Keyword(s):  
Dynkin Diagram ◽  
Type A ◽  
Affine Algebra ◽  
Large Rank ◽  
Rigged Configurations ◽  
International Audience

International audience For an affine algebra of nonexceptional type in the large rank we show the fermionic formula depends only on the attachment of the node 0 of the Dynkin diagram to the rest, and the fermionic formula of not type $A$ can be expressed as a sum of that of type $A$ with Littlewood–Richardson coefficients. Combining this result with theorems of Kirillov–Schilling–Shimozono and Lecouvey–Okado–Shimozono, we settle the $X=M$ conjecture under the large rank hypothesis. Pour une algèbre affine de type non-exceptionnel de grand rang nous prouvons que la formule fermionique dépend seulement du voisinage du nœud 0 dans le diagramme de Dynkin, et également que la formule fermionique en type autre que $A$ peut être exprimée comme combinaison de celles de type $A$ avec des coefficients de Littlewood–Richardson. Combinant ce résultat avec des théorèmes de Kirillov–Schilling–Shimozono et de Lecouvey–Okado–Shimozono, nous résolvons la conjecture $X=M$ lorsque le rang est grand.

scholarly journals A bijection between noncrossing and nonnesting partitions of types A and B

2009 ◽  
Vol DMTCS Proceedings vol. AK,... (Proceedings) ◽  
Author(s):  
Ricardo Mamede
Keyword(s):  
Type A ◽  
Binomial Coefficient ◽  
Catalan Number ◽  
Noncrossing Partitions ◽  
Il Y A ◽  
International Audience

International audience The total number of noncrossing partitions of type $\Psi$ is the $n$th Catalan number $\frac{1}{ n+1} \binom{2n}{n}$ when $\Psi =A_{n-1}$, and the binomial coefficient $\binom{2n}{n}$ when $\Psi =B_n$, and these numbers coincide with the correspondent number of nonnesting partitions. For type $A$, there are several bijective proofs of this equality; in particular, the intuitive map, which locally converts each crossing to a nesting, is one of them. In this paper we present a bijection between nonnesting and noncrossing partitions of types $A$ and $B$ that generalizes the type $A$ bijection that locally converts each crossing to a nesting. Le nombre total des partitions non-croisées du type $\Psi$ est le $n$-ème nombre de Catalan $\frac{1}{ n+1} \binom{2n}{n}$ si $\Psi =A_{n-1}$, et le coefficient binomial $\binom{2n}{n}$ si $\Psi =B_n$, et ces nombres son coïncidents avec le nombre correspondant des partitions non-emboîtées. Pour le type $A$, il y a plusieurs preuves bijectives de cette égalité; en particulier, la intuitive fonction, qui convertit localement chaque croisée en une emboîtée, c'est un d'entre eux. Dans ce papier nous présentons une bijection entre partitions non-croisées et non-emboîtées des types $A$ et $B$ qui généralise la bijection du type $A$ qui localement convertit chaque croisée en une emboîtée.

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