Results 31 to 40 of about 159 (46)

Subgroup posets, Bredon cohomology and equivariant Euler characteristics [PDF]

, 2012
For a discrete group $\Gamma$ satisfying some finiteness conditions we give a Bredon projective resolution of the trivial module in terms of projective covers of the chain complex associated to certain posets of subgroups. We use this to give new results
Martínez-Pérez, Conchita
core  

$S$-almost perfect commutative rings

, 2019
Given a multiplicative subset $S$ in a commutative ring $R$, we consider $S$-weakly cotorsion and $S$-strongly flat $R$-modules, and show that all $R$-modules have $S$-strongly flat covers if and only if all flat $R$-modules are $S$-strongly flat.
Bazzoni, Silvana, Positselski, Leonid
core   +1 more source

Contraherent cosheaves [PDF]

, 2017
Contraherent cosheaves are globalizations of cotorsion (or similar) modules over commutative rings obtained by gluing together over a scheme. The category of contraherent cosheaves over a scheme is a Quillen exact category with exact functors of infinite
Positselski, Leonid
core  

Curved differential graded algebras and corings

, 2013
A relationship between curved differential algebras and corings is established and explored. In particular it is shown that the category of semi-free curved differential graded algebras is equivalent to the category of corings with surjective counits ...
Brzeziński, Tomasz
core  

Compact generators of the contraderived category of contramodules

LaTeX 2e with mathrsfs and xy-pic; 54 pages, 6 commutative ...
Positselski, Leonid, Stovicek, Jan
openaire   +2 more sources

Contramodules for algebraic groups: Induction and projective covers

Journal of Algebra
In this paper we will investigate contramodules for algebraic groups. Namely, we give contra-analogs to two 20th century results about comodules. Firstly, we show that induction of contramodules over coordinate rings of algebraic groups is exact if and only if the associated quotient variety is affine.
openaire   +2 more sources

Entwined comodules and contramodules over coalgebras with several objects: Frobenius, separability and Maschke theorems

Journal of Algebra
We study module like objects over categorical quotients of algebras by the action of coalgebras with several objects. These take the form of ``entwined comodules'' and ``entwined contramodules'' over a triple $(\mathscr C,A,ψ)$, where $A$ is an algebra, $\mathscr C$ is a coalgebra with several objects and $ψ$ is a collection of maps that ``entwines'' $\
Abhishek Banerjee, Surjeet Kour
openaire   +2 more sources

Cup products in Hopf cyclic cohomology with coefficients in contramodules

, 2010
We use stable anti Yetter-Drinfeld contramodules to improve the cup products in Hopf cyclic cohomology. The improvement fixes the lack of functoriality of the cup products previously defined and show that the cup products are sensitive to the coefficients.
openaire   +2 more sources

A contramodule generalization of Neeman’s flat and projective module theorem

Journal of Homotopy and Related Structures
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 of projective left $\mathfrak R$-contramodules is equivalent to the derived category of the exact category of ...
openaire   +3 more sources

Galois measurings for noncommutative base change of entwined contramodule and entwined comodule categories

We study the noncommutative base change of an entwining structure $(A,C,ψ)$ by a Grothendieck category $\mathfrak S$, using two module like categories. These are the categories of entwined comodule objects and entwined contramodule objects in $\mathfrak S$ over the entwining structure $(A,C,ψ)$.
Ahuja, Divya, Banerjee, Abhishek, Kour, Surjeet   +2 more
openaire   +2 more sources