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We explain how to attach a coalgebra $\mathcal C$ over a field $k$ to a small $k$-linear category $\mathsf E$ satisfying suitable finiteness conditions. In this context, we study full-and-faithfulness of the contramodule forgetful functor,…

Category Theory · Mathematics 2023-10-12 Leonid Positselski

We classify localising subcategories of the stable module category of a finite group that are closed under tensor product with simple (or, equivalently all) modules. One application is a proof of the telescope conjecture in this context.…

Representation Theory · Mathematics 2011-04-18 Dave Benson , Srikanth B. Iyengar , Henning Krause

In this dissertation, we compare the "classical" homology of an $\omega$-category (defined as the homology of its Street nerve) with its polygraphic homology. More precisely, we prove that both homologies generally do not coincide and call…

Category Theory · Mathematics 2021-04-27 Léonard Guetta

To any dg-category $T$ (over some base ring $k$), we define a $D^{-}$-stack $\mathcal{M}_{T}$ in the sense of \cite{hagII}, classifying certain $T^{op}$-dg-modules. When $T$ is saturated, $\mathcal{M}_{T}$ classifies compact objects in the…

Algebraic Geometry · Mathematics 2007-05-23 B. Toen , M. Vaquie

We prove that one can realize certain triangulated subcategories of the singularity category of a complete intersection as homotopy categories of matrix factorizations. Moreover, we prove that for any commutative ring and non-zerodivisor,…

Commutative Algebra · Mathematics 2015-09-15 Petter Andreas Bergh , David A. Jorgensen

Let $R$ be an associative ring with identity. This paper investigates the structure of the monomorphism category of large $R$-modules and establishes connections with the category of contravariant functors defined on finitely presented…

Representation Theory · Mathematics 2025-04-11 Rasool Hafezi , Javad Asadollahi , Razieh Vahed , Yi Zhang

We show that, up to Morita equivalence, any finite-dimensional algebra with a suitable homological system, admits an exact Borel subalgebra. This generalizes a theorem by Koenig, K\"ulshammer and Ovsienko, which holds for quasi-hereditary…

Representation Theory · Mathematics 2020-12-29 Raymundo Bautista Ramos , Jesús Efrén Pérez Terrazas , Leonardo Salmerón Castro

Let $\mathcal C$ be a class of modules and $\mathcal L = \varinjlim \mathcal C$ the class of all direct limits of modules from $\mathcal C$. The class $\mathcal L$ is well understood when $\mathcal C$ consists of finitely presented modules:…

Rings and Algebras · Mathematics 2022-05-23 Leonid Positselski , Pavel Prihoda , Jan Trlifaj

Let $R$ be a commutative ring with unit. We consider the homotopy theory of the category of spectral sequences of $R$-modules with the class of weak equivalences given by those morphisms inducing a quasi-isomorphism at a certain fixed page.…

Algebraic Topology · Mathematics 2023-02-22 Muriel Livernet , Sarah Whitehouse

We introduce a notion of $\Theta$-categories, which is a refinement of the notion of symmetric monoidal $\infty$-categories. We use this notion to prove a Tannakian duality statement, relating $\Theta$-categories with fpqc-stacks by means…

Algebraic Geometry · Mathematics 2025-08-06 Joost Nuiten , Bertrand Toen

In the first part of the paper we associate a pre-additive category $\mathcal{C}(\Sigma)$ to a closed oriented surface $\Sigma$, called the {\em contact category} and constructed from contact structures on $\Sigma\times[0,1]$. There are…

Symplectic Geometry · Mathematics 2021-05-24 Ko Honda , Yin Tian

We prove explicit and elementary formulas for the group homology and cohomology of a finite group with coefficients in any module. We describe in elementary terms the cohomology algebra $H^*(G,k)$ as a graded algebra for a finite group $G$…

Group Theory · Mathematics 2015-07-16 Sergei O. Ivanov , Nikolay N. Mostovsky

It is proved that the sum of the Loewy lengths of the homology modules of a finite free complex F over a local ring R is bounded below by a number depending only on R. This result uncovers, in the structure of modules of finite projective…

Commutative Algebra · Mathematics 2010-05-20 L. L. Avramov , R. -O. Buchweitz , S. B. Iyengar , C. Miller

For a Cohen-Macaulay ring $R$, we exhibit the equivalence of the bounded derived categories of certain resolving subcategories, which, amongst other results, yields an equivalence of the bounded derived category of finite length and finite…

K-Theory and Homology · Mathematics 2015-05-26 William Sanders , Sarang Sane

For a finite dimensional algebra $A$, we prove that the bounded homotopy category of projective $A$-modules and the bounded derived category of $A$-modules are dual to each other via certain categories of locally-finite cohomological…

Rings and Algebras · Mathematics 2018-10-09 Xiao-Wu Chen

We construct a long exact sequence involving the homology of an FI-module. Using the long exact sequence, we give two methods to bound the Castelnuovo-Mumford regularity of an FI-module which is generated and related in finite degree. We…

Representation Theory · Mathematics 2016-04-13 Wee Liang Gan

Watts's Theorem says that a right exact functor F:Mod R-->Mod S that commutes with direct sums is isomorphic to -\otimes_R B where B is the R-S-bimodule FR. The main result in this paper is the following: if A is a cocomplete abelian…

Rings and Algebras · Mathematics 2008-06-05 A. Nyman , S. Paul Smith

Let $G$ be a finite group. We show that the order of the subgroup generated by coprime $\gamma_k$-commutators (respectively $\delta_k$-commutators) is bounded in terms of the size of the set of coprime $\gamma_k$-commutators (respectively…

Group Theory · Mathematics 2019-02-20 Cristina Acciarri , Pavel Shumyatsky , Anitha Thillaisundaram

We prove that for any finite-dimensional differential graded algebra with separable semisimple part the category of perfect modules is equivalent to a full subcategory of the category of perfect complexes on a smooth projective scheme with…

Algebraic Geometry · Mathematics 2020-03-18 Dmitri Orlov

This paper builds on top of arXiv:2306.02734. We consider a complete, separated topological ring $\mathfrak R$ with a countable base of neighborhoods of zero consisting of open two-sided ideals. The main result is that the homotopy category…

Rings and Algebras · Mathematics 2025-11-12 Leonid Positselski