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In pursuit of a noncommutative spectrum functor, we argue that the Heyneman-Sweedler finite dual coalgebra can be viewed as a quantization of the maximal spectrum of a commutative affine algebra, integrating prior perspectives of Takeuchi,…

Rings and Algebras · Mathematics 2024-01-30 Manuel L. Reyes

We generalize Brenner and Butler's Theorem as well as Happel's Theorem on the equivalences induced by a finitely generated tilting module over artin algebras, to the case of an infinitely generated tilting module over an arbitrary…

Rings and Algebras · Mathematics 2019-12-16 Silvana Bazzoni

For any finitely generated abelian group $Q$, we reduce the problem of classification of $Q$-graded simple Lie algebras over an algebraically closed field of "good" characteristic to the problem of classification of gradings on simple Lie…

Representation Theory · Mathematics 2016-11-29 Volodymyr Mazorchuk , Kaiming Zhao

We consider hereditary Artin algebras over arbitrary fields and prove that there is a natural bijection between the Weyl groups and the sets of full additive cofinite submodule closed subcategories of the module categories. While Oppermann,…

Representation Theory · Mathematics 2017-10-17 Apolonia Gottwald

We study coherent $I$-indexed algebras and associated noncommutative projective schemes, where the index set $I$ is a locally finite directed poset. Our main result is a characterisation of such noncommutative projective schemes in terms of…

Rings and Algebras · Mathematics 2025-07-21 Jackson Ryder

We introduce the notion of the $\infty$-category of (complete) derived $G$-graded modules over a $G$-graded ring $R$ for a torsion-free abelian group $G$, and we study its foundational properties. Moreover, we prove a categorical…

Commutative Algebra · Mathematics 2026-04-06 Ryo Ishizuka , Shou Yoshikawa

In this note, we show that every Noetherian graded ring with an affine degree zero part is affine. As a result, a Noetherian graded Hopf algebra whose degree zero component is a commutative or a cocommutative Hopf subalgebra is affine.…

Rings and Algebras · Mathematics 2025-03-18 Huan Jia , Yinhuo Zhang

In a perfect category every object has a minimal projective resolution. We give a criterion for the category of modules over a categorygraded algebra to be perfect.

Category Theory · Mathematics 2016-02-09 Ana Paula Santana , Ivan Yudin

Using the Nakayama duality induced by a Nakayama functor, we provide a novel and concise account of the existence of Auslander-Reiten dualities and almost split sequences in abelian categories with enough projective objects or enough…

Representation Theory · Mathematics 2025-12-25 Zetao Lin , Shiping Liu

The notion of gluing of abelian categories was introduced by Kazhdan and Laumon in an attempt of another geometric construction of representations of finite Chevalley groups; the approach was later developed by Polishchuk and Braverman. We…

Representation Theory · Mathematics 2009-09-04 Roman Bezrukavnikov , Alexander Braverman , Leonid Positselskii

Let $\Lambda$ be a $\mathbb{Z}$-graded artin algebra. Two classical results of Gordon and Green state that if $\Lambda$ has only finitely many indecomposable gradable modules, up to isomorphism, then $\Lambda$ has finite representation…

Representation Theory · Mathematics 2018-08-07 Alex Dugas

We study a class of noncommutative surfaces and their higher dimensional analogues which provide answers to several open questions in noncommutative projective geometry. Specifically, we give the first known graded algebras which are…

Rings and Algebras · Mathematics 2007-05-23 Daniel Rogalski

Let $Q$ be a finite acyclic quiver and $A_Q$ the cluster algebra of $Q$. It is well-known that for each field $k$, the additive equivalence classes of support tilting $kQ$-modules correspond bijectively with the clusters of $A_Q$. The aim…

Representation Theory · Mathematics 2025-04-04 Osamu Iyama , Yuta Kimura

We reconsider a classical theorem by Bican and El Bashir, which guarantees the existence of non-trivial relatively pure submodules in a module category over a ring with unit. Our aim is to generalize the theorem to module categories over…

Category Theory · Mathematics 2013-10-31 Alexander Schmeding

This is the second in a series of papers intended to set up a framework to study categories of modules in the context of non-commutative geometries. In \cite{mem} we introduced the basic DG category $\Pc_{\A^\bullet}$, the perfect category…

Quantum Algebra · Mathematics 2007-05-23 Jonathan Block

In the paper "Cotorsion Pairs in C(R-Mod)", the authors construct an abelian model structure on the category of chain complexes Ch(R), where the class of cofibrant objects is given by the class of degreewise projective chain complexes.…

Category Theory · Mathematics 2012-07-03 Marco Pérez

We show that if a flat group scheme acts properly, with finite stabilizers, on an algebraic space, then a quotient exists as a separated algebraic space. More generally we show any flat groupid for which the family of stabilizers is finite…

alg-geom · Mathematics 2008-02-03 Sean Keel , Shigefumi Mori

Extending the Wedderburn-Artin theory of (classically) semisimple associative rings to the realm of topological rings with right linear topology, we show that the abelian category of left contramodules over such a ring is split…

Category Theory · Mathematics 2022-06-15 Leonid Positselski , Jan Stovicek

We show that for a given exact category, there exists a bijection between semibricks (pairwise Hom-orthogonal set of bricks) and length wide subcategories (exact extension-closed length abelian subcategories). In particular, we show that a…

Category Theory · Mathematics 2022-08-08 Haruhisa Enomoto

Extension conjecture states that if a simple module over an artin algebra has nonzero first self-extension group then it has nonzero i-th self-extension group for infinitely many positive integers i. It is shown by recollement of…

Representation Theory · Mathematics 2014-07-08 Yang Han