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Existence of proper Gorenstein projective resolutions and Tate cohomology is proved
over rings with a dualizing complex. The proofs are based on Bousfield Localization which is originally a method from algebraic topology.
Let be a ring. In two previous articles [12, 14] we studied the homotopy category of projective -modules. We produced a set of generators for this category, proved that the category is -compactly generated for any ring , and showed that it need not always be compactly generated, but is for sufficiently nice . We furthermore analyzed the inclusion and the orthogonal subcategory . And we even showed that the inclusion has a right adjoint; this forces some natural map to be an equivalence...
Nous nous intéressons à la question de l’existence de familles de Hurwitz au-dessus d’un espace de modules de revêtements de la droite. On sait que de telles familles existent dans le cas où les revêtements n’ont pas d’automorphismes. Dans le cas général, il y a une obstruction cohomologique, de nature non-abélienne. Nous donnons une double description de cette obstruction : la première en termes de gerbe, l’outil le mieux adapté à des situations cohomologiques non-abéliennes et la deuxièmes en...
For any module M over an associative ring R, let σ[M] denote the smallest Grothendieck subcategory of Mod-R containing M. If σ[M] is locally finitely presented the notions of purity and pure injectivity are defined in σ[M]. In this paper the relationship between these notions and the corresponding notions defined in Mod-R is investigated, and the connection between the resulting Ziegler spectra is discussed. An example is given of an M such that σ[M] does not contain any non-zero finitely presented...
We introduce the notions of silting comodules and finitely silting comodules in quasi-finite category, and study some properties of them. We investigate the torsion pair and dualities which are related to finitely silting comodules, and give the equivalences among silting comodules, finitely silting comodules, tilting comodules and finitely tilting comodules.
We study the relations between finitistic dimensions and restricted injective dimensions. Let be a ring and a left -module with . If is selforthogonal, then we show that . Moreover, if is a left noetherian ring and is a finitely generated left -module with finite injective dimension, then . Also we show by an example that the restricted injective dimensions of a module may be strictly smaller than the Gorenstein injective dimension.
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