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We characterize the indecomposable transjective modules over an arbitrary cluster-tilted algebra that do not lie on a local slice, and we provide a sharp upper bound for the number of (isoclasses of) these modules.

Representation Theory · Mathematics 2016-06-17 Ibrahim Assem , Ralf Schiffler , Khrystyna Serhiyenko

We define modular Terwilliger algebras of association schemes, Terwilliger algebras over a positive characteristic field, and consider basic properties. We give a condition for the modular Terwilliger algebra to be non-semisimple. We show…

Combinatorics · Mathematics 2021-09-06 Akihide Hanaki

Let $A$ be a hereditary algebra. We construct a fundamental domain for the cluster category of $A$ inside the category of modules over the duplicated algebra $\bar{A}$ of $A$. We then prove that there exists a bijection between the tilting…

Representation Theory · Mathematics 2007-05-23 Ibrahim Assem , Thomas Brüstle , Ralf Schiffler , Gordana Todorov

Given a finite group G, let cd(G) denote the set of degrees of the irreducible complex characters of G. The character degree graph of G is defined as the simple undirected graph whose vertices are the prime divisors of the numbers in cd(G),…

Group Theory · Mathematics 2018-09-28 Zeinab Akhlaghi , Carlo Casolo , Silvio Dolfi , Emanuele Pacifici , Lucia Sanus

Let $A$ be a finite dimensional algebra over an algebraically closed field $k$, and $M$ be a partial tilting $A$-module. We prove that the Bongartz $\tau$-tilting complement of $M$ coincides with its Bongartz complement, and then we give a…

Representation Theory · Mathematics 2015-12-14 Shen Li , Shunhua Zhang

The symplectic blob algebra is a physically motivated quotient of the Hecke algebra $H(\tilde{C}_n)$ with a diagram calculus. We find the blocks for the symplectic blob algebra for all specialisations of its parameters over the complex…

Representation Theory · Mathematics 2024-07-11 Oliver H. King , Paul P. Martin , Alison E. Parker

We study five different types of the homology of a Lie algebra over a commutative ring which are naturally isomorphic over fields. We show that they are not isomorphic over commutative rings, even over $\mathbb Z,$ and study connections…

K-Theory and Homology · Mathematics 2022-01-19 Sergei O. Ivanov , Fedor Pavutnitskiy , Vladislav Romanovskii , Anatolii Zaikovskii

Let Q be a finite quiver without oriented cycles, and let $\Lambda$ be the corresponding preprojective algebra. Let g be the Kac-Moody Lie algebra with Cartan datum given by Q, and let W be its Weyl group. With w in W is associated a…

Representation Theory · Mathematics 2019-03-05 Christof Geiß , Bernard Leclerc , Jan Schröer

We can define the adjacency algebra of an association scheme over arbitrary field. It is not always semisimple over a field of positive characteristic. The structures of adjacency algebras over a field of positive characteristic have not…

Combinatorics · Mathematics 2015-06-11 Osamu Shimabukuro

Let Q be a finite quiver without oriented cycles, and let $\Lambda$ be the associated preprojective algebra. To each terminal representation M of Q (these are certain preinjective representations), we attach a natural subcategory $C_M$ of…

Representation Theory · Mathematics 2010-08-02 Christof Geiss , Bernard Leclerc , Jan Schröer

We show that the number of parameters for CM-modules of prescribed rank is semi-continuous in families of CM rings of Krull dimension 1. This transfers a result of Knoerrer from the commutative to the not necessarily commutative case. For…

alg-geom · Mathematics 2008-02-03 Y. A. Drozd , G. -M. Greuel

Let H be a separable, infinite dimensional Hilbert space and let S be a countable subset of H. Then most positive operators on H have the property that every nonzero vector in the span of S is cyclic, in the sense that the set of operators…

Functional Analysis · Mathematics 2007-05-23 Nik Weaver

M. Hochster defines an invariant namely $\Theta(M,N)$ associated to two finitely generated module over a hyper-surface ring $R=P/f$, where $P=k\{x_0,...,x_n\}$ or $k[X_0,...,x_n]$, for $k$ a field and $f$ is a germ of holomorphic function…

Algebraic Geometry · Mathematics 2017-02-10 Mohammad Reza Rahmati

Let H be a semisimple algebaric group and let X be a smooth projective curve defined over an algebraically closed field k. In the first part of this paper we show that the moduli of semistable principal H-bundles exists once given a…

Algebraic Geometry · Mathematics 2007-05-23 V. Balaji , A. J. Parameswaran

We study monoidal categorifications of certain monoidal subcategories $\mathcal{C}_J$ of finite-dimensional modules over quantum affine algebras, whose cluster algebra structures coincide and arise from the category of finite-dimensional…

Quantum Algebra · Mathematics 2019-04-03 Masaki Kashiwara , Myungho Kim , Se-jin Oh , Euiyong Park

Let $X$ be a smooth, irreducible, projective algebraic surface, and let $\alpha \in \mathbb{Q}[m]_{>0}$ be a polynomial. In this paper, we determine topological and geometric properties of the moduli space of $\alpha$-stable coherent…

Algebraic Geometry · Mathematics 2026-03-23 L. Costa , I. Macías Tarrío , L. Roa-Leguizamón

We describe the ordinary characters of trivial source modules lying in blocks with cyclic defect groups relying on their recent classification in terms of paths on the Brauer tree by G.~Hiss and the second author. In particular, we show how…

Representation Theory · Mathematics 2020-04-07 Shigeo Koshitani , Caroline Lassueur

It is shown that path algebras modulo relations of the form $\Lambda = KQ/I$, where $Q$ is a quiver, $K$ a coefficient field, and $I \subseteq KQ$ the ideal generated by all paths of a given length, can be readily analyzed homologically,…

Representation Theory · Mathematics 2014-07-11 A. Dugas , B. Huisgen-Zimmermann , J. Learned

It is proved that the K_0-group of a cluster C*-algebra is isomorphic to the corresponding cluster algebra. As a corollary, one gets a shorter proof of the positivity conjecture for cluster algebras. As an example, we consider a cluster…

Operator Algebras · Mathematics 2020-09-07 Igor Nikolaev

Let $\mathcal{C}$ be a Hom-finite triangulated 2-Calabi-Yau category with a cluster tilting object. Under some constructibility assumptions on $\mathcal{C}$ which are satisfied for instance by cluster categories, by generalized cluster…

Representation Theory · Mathematics 2014-02-26 Yann Palu