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Stable short exact sequences and the maximal exact structure of an additive category

Wolfgang Rump (2015)

Fundamenta Mathematicae

It was recently proved that every additive category has a unique maximal exact structure, while it remained open whether the distinguished short exact sequences of this canonical exact structure coincide with the stable short exact sequences. The question is answered by a counterexample which shows that none of the steps to construct the maximal exact structure can be dropped.

Strict Mittag-Leffler conditions and locally split morphisms

Yanjiong Yang, Xiaoguang Yan (2018)

Czechoslovak Mathematical Journal

In this paper, we prove that any pure submodule of a strict Mittag-Leffler module is a locally split submodule. As applications, we discuss some relations between locally split monomorphisms and locally split epimorphisms and give a partial answer to the open problem whether Gorenstein projective modules are Ding projective.

Structure of flat covers of injective modules

Sh. Payrovi, M. Akhavizadegan (2003)

Colloquium Mathematicae

The aim of this paper is to discuss the flat covers of injective modules over a Noetherian ring. Let R be a commutative Noetherian ring and let E be an injective R-module. We prove that the flat cover of E is isomorphic to p A t t R ( E ) T p . As a consequence, we give an answer to Xu’s question [10, 4.4.9]: for a prime ideal p, when does T p appear in the flat cover of E(R/m̲)?

Sugli ideali di Borel

Maria Grazia Marinari (2001)

Bollettino dell'Unione Matematica Italiana

In this note we study some algebraic properties of Borel Ideals in the ring of polynomials over an effective field of characteristic zero by using a suitable partial order relation defined on the set of terms of each degree. In particular, in the three variable case, we characterize all the 0-dimensional Borel ideals corresponding to an admissible h -vector and their minimal free resolutions.

Sur le Topos infinitésimal p -adique d’un schéma lisse I

Alberto Arabia, Zoghman Mebkhout (2010)

Annales de l’institut Fourier

Afin de disposer des opérations cohomologiques aussi souples que possible pour la cohomologie de de Rham p -adique, le but principal de ce mémoire est de résoudre intrinsèquement du point de vue cohomologique le problème des relèvements des schémas lisses et de leurs morphismes de la caractéristique p > 0 à la caractéristique nulle ce qui a été l’une des difficultés centrales de la théorie de la cohomologie de de Rham des schémas algébriques en caractéristique positive depuis le début. Nous montrons...

Syzygies of modules and applications to propagation of regularity phenomena.

Alex Meril, Daniele C. Struppa (1990)

Publicacions Matemàtiques

Propagation of regularity is considered for solutions of rectangular systems of infinite order partial differential equations (resp. convolution equations) in spaces of hyperfunctions (resp. C∞ functions and distributions). Known resulys of this kind are recovered as particular cases, when finite order partial differential equations are considered.

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