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The category of groupoid graded modules

Patrik Lundström (2004)

Colloquium Mathematicae

We introduce the abelian category R-gr of groupoid graded modules and give an answer to the following general question: If U: R-gr → R-mod denotes the functor which associates to any graded left R-module M the underlying ungraded structure U(M), when does either of the following two implications hold: (I) M has property X ⇒ U(M) has property X; (II) U(M) has property X ⇒ M has property X? We treat the cases when X is one of the properties: direct summand, free, finitely generated, finitely presented,...

The quasi-hereditary algebra associated to the radical bimodule over a hereditary algebra

Lutz Hille, Dieter Vossieck (2003)

Colloquium Mathematicae

Let Γ be a finite-dimensional hereditary basic algebra. We consider the radical rad Γ as a Γ-bimodule. It is known that there exists a quasi-hereditary algebra 𝓐 such that the category of matrices over rad Γ is equivalent to the category of Δ-filtered 𝓐-modules ℱ(𝓐,Δ). In this note we determine the quasi-hereditary algebra 𝓐 and prove certain properties of its module category.

The symplectic Gram-Schmidt theorem and fundamental geometries for 𝒜 -modules

Patrice P. Ntumba (2012)

Czechoslovak Mathematical Journal

Like the classical Gram-Schmidt theorem for symplectic vector spaces, the sheaf-theoretic version (in which the coefficient algebra sheaf 𝒜 is appropriately chosen) shows that symplectic 𝒜 -morphisms on free 𝒜 -modules of finite rank, defined on a topological space X , induce canonical bases (Theorem 1.1), called symplectic bases. Moreover (Theorem 2.1), if ( , φ ) is an 𝒜 -module (with respect to a -algebra sheaf 𝒜 without zero divisors) equipped with an orthosymmetric 𝒜 -morphism, we show, like in the classical...

Thick subcategories of the stable module category

D. Benson, Jon Carlson, Jeremy Rickard (1997)

Fundamenta Mathematicae

We study the thick subcategories of the stable category of finitely generated modules for the principal block of the group algebra of a finite group G over a field of characteristic p. In case G is a p-group we obtain a complete classification of the thick subcategories. The same classification works whenever the nucleus of the cohomology variety is zero. In case the nucleus is nonzero, we describe some examples which lead us to believe that there are always infinitely many thick subcategories concentrated...

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