Special precovering classes in comma categories

J Hu, H Zhu - Science China Mathematics, 2022 - Springer
… not only give rise to adjoint functors for constructing recollements … modules, complete
cotorsion pairs make it possible to produce special preenvelopes once we know special precovers

fpn-injective and fpn-flat modules

J Wei, Y Zhang - Georgian Mathematical Journal, 2015 - degruyter.com
preenvelope). We also study the exchange properties of … with ∈ C is a monic C-precover
of , then it is a monic C-cover of … As to the second claim, note that we have an adjoint

Approximations by maximal Cohen–Macaulay modules

H Holm - Pacific Journal of Mathematics, 2015 - msp.org
module has a special maximal CM precover. In this paper, we prove the existence of special
maximal CM preenvelopes … , which we claim is a left adjoint of the inclusion G : MCM → mod…

[PDF][PDF] APPROXIMATIONS OF MODULES (LECTURE NOTES FOR NMAG531)

JAN TRLIFAJ - 2023 - karlin.mff.cuni.cz
… This fact – discovered by Salce [34] – says that the mutually dual categorical notions of a
special precover and a special preenvelope are tied up by the homological tie of a cotorsion …

Covers and direct limits: a contramodule-based approach

S Bazzoni, L Positselski - Mathematische Zeitschrift, 2021 - Springer
… -modules. Subsequently, in 1981 Enochs proved that any precovering class of modules closed
… L\) can be naturally extended to a pair of adjoint functors \(\Phi :\mathsf B\longrightarrow \…

Cotorsion pairs and approximation classes over formal triangular matrix rings

L Mao - Journal of Pure and Applied Algebra, 2020 - Elsevier
… is devoted to preenvelopes and precovers of modules over a … of left A-modules and D be a
class of left B-modules, we prove … to see that p is a left adjoint of q and h is a right adjoint of q. …

On exact categories and applications to triangulated adjoints and model structures

M Saorín, J Šťovíček - Advances in Mathematics, 2011 - Elsevier
module categories. In particular we prove that every deconstructible class of modules is
precovering… M is necessarily an X-precover while the inflation M ↣ Y is a Y-preenvelope. We will …

Absolutely s-Pure Modules and Neat-Flat Modules

E Büyükaşık, Y Durğun - Communications in Algebra, 2015 - Taylor & Francis
… The rings whose simple right modules have a projective preenvelope are … homomorphism
φ: A → M is an ℳ-precover of M if A ∈ ℳ and the abelian … by the standard adjoint isomorphism. …

[PDF][PDF] On mininjective and min-flat modules

LX Mao - Publ. Math. Debrecen, 2008 - scholar.archive.org
… A C-precover φ : C → M of M is said to be a C-cover if every … Dually we have the definitions
of a C-preenvelope and a C-… precovers and the cokernels of min-flat preenvelopes, we …

Gorenstein flat precovers and Gorenstein injective preenvelopes in Grothendieck categories

E Enochs, JR García Rozas, L Oyonarte, B Torrecillas - 2019 - projecteuclid.org
… ) in this category to be precovering, we need the class of flat discrete modules to be closed
… tensor product of modules) is precovering (see [2, Corollary 4.8]). Our type of precovers are …