WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

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Author: search.filters.author.Buyukasik, Engin

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Now showing 1 - 7 of 7
  • Article
    Citation - WoS: 1
    Modules Whose Maximal Submodules Have Τ-Supplements
    (Luhansk Taras Shevchenko Natl Univ, 2010) Buyukasik, Engin
    Let R be a ring and tau be a preradical for the category of left R-modules. In this paper, we study on modules whose maximal submodules have tau-supplements. We give some characterizations of these modules interms their certain submodules, so called tau-localsubmodules. For some certain preradicals tau, i.e. tau=delta and idempotent tau, we prove that every maximal submodule of M has a tau-supplement if and only if every cofinite submodule of M has a tau-supplement. For a radical tau onR-Mod, we prove that, forevery R-module every submodule is a tau-supplement if and only if R/tau(R) is semisimple and tau is hereditary
  • Article
    Projectivity and Quasi-Projectivity With Respect To Epimorphisms To Simple Modules
    (World Scientific Publ Co Pte Ltd, 2025) Alagoz, Yusuf; Alizade, Rafail; Buyukasik, Engin
    Using the notion of relative max-projectivity, max-projectivity domain of a module is investigated. Such a domain includes the class of all modules whose maximal submodules are direct summands (this class denoted as MDMod -R). We call a module max-p-poor if its max-projectivity domain is exactly the class MDMod -R. We establish the existence of max-p-poor modules over any ring. Furthermore, we study commutative rings whose simple modules are projective or max-p-poor. Additionally, we determine the right Noetherian rings for which all right modules are projective or p-poor. Max-p-poor abelian groups are fully characterized and shown to coincide precisely with p-poor abelian groups. We also further investigate modules that are max-projective relative to themselves, which are known as simple-quasi-projective modules. Several properties of these modules are provided, and the structure of certain classes of simple-quasi-projective modules is determined over specific commutative rings including the ring of integers and valuation domains.
  • Article
    Subinjectivity Relative To Cotorsion Pairs
    (MDPI, 2025) Alagoz, Yusuf; Alizade, Rafail; Buyukasik, Engin; Rozas, Juan Ramon Garcia; Oyonarte, Luis
    In this paper, we define and study the X-subinjectivity domain of a module M where X=(A,B) is a complete cotorsion pair, which consists of those modules N such that, for every extension K of N with K/N in A, any homomorphism f:N -> M can be extended to a homomorphism g:K -> M. This approach allows us to characterize some classical rings in terms of these domains and generalize some known results. In particular, we classify the rings with X-indigent modules-that is, the modules whose X-subinjectivity domains are as small as possible-for the cotorsion pair X=(FC,FI), where FI is the class of FP-injective modules. Additionally, we determine the rings for which all (simple) right modules are either X-indigent or FP-injective. We further investigate X-indigent Abelian groups in the category of torsion Abelian groups for the well-known example of the flat cotorsion pair X=(FL,EC), where FL is the class of flat modules.
  • Article
    Rings Whose Mininjective Modules Are Injective
    (Taylor & Francis inc, 2025) Alagoz, Yusuf; Benli-Goral, Sinem; Buyukasik, Engin; Garcia Rozas, Juan Ramon; Oyonarte, Luis
    The main goal of this paper is to characterize rings over which the mininjective modules are injective, so that the classes of mininjective modules and injective modules coincide. We show that these rings are precisely those Noetherian rings for which every min-flat module is projective and we study this characterization in the cases when the ring is Kasch, commutative and when it is quasi-Frobenius. We also treat the case of nxn upper triangular matrix rings, proving that their mininjective modules are injective if and only if n=2. We use the developed machinery to find a new type of examples of indigent modules (those whose subinjectivity domain contains only the injective modules), whose existence is known, so far, only in some rather restricted situations.
  • Article
    Virtually Regular Modules
    (World Scientific Publ Co Pte Ltd, 2025) Buyukasik, Engin; Demir, Ozlem Irmak
    In this paper, we call a right module M (strongly) virtually regular if every (finitely generated) cyclic submodule of M is isomorphic to a direct summand of M. M is said to be completely virtually regular if every submodule of M is virtually regular. In this paper, characterizations and some closure properties of the aforementioned modules are given. Several structure results are obtained over commutative rings. In particular, the structures of finitely presented (strongly) virtually regular modules and completely virtually regular modules are fully determined over valuation domains. Namely, for a valuation domain R with the unique nonzero maximal ideal P, we show that finitely presented (strongly) virtually regular modules are free if and only if P is not principal; and that P = Rp is principal if and only if finitely presented virtually regular modules are of the form R-n circle plus (R/Rp)(n)(1) circle plus (R/Rp(2))(n)(2) circle plus center dot center dot center dot circle plus (R/Rp(k))(n)(k) for nonnegative integers n, k, n(1), n(2),...,n(k). Similarly, we prove that P = Rp is principal if and only if finitely presented strongly virtually regular modules are of the form R-n circle plus (R/Rp)(m), where m,n are nonnegative integers. We also obtain that, R admits a nonzero finitely presented completely virtually regular module M if and only if P = Rp is principal. Moreover, for a finitely presented R-module M, we prove that: (i) if R is not a DVR, then M is completely virtually regular if and only if M congruent to( R/Rp)(m); and (ii) if R is a DVR, then M is completely virtually regular if and only if M congruent to R-n circle plus ( R/Rp)(m). Finally, we obtain a characterization of finitely generated virtually regular modules over the ring of integers.
  • Article
    On the Rings Whose Injective Right Modules Are Max-Projective
    (World Scientific Publ Co Pte Ltd, 2024) Alagoz, Yusuf; Buyukasik, Engin; Yurtsever, Haydar Baran
    Recently, right almost-QF (respectively, max-QF) rings that is the rings whose injective right modules are R-projective (respectively, max-projective) were studied by the first two authors. In this paper, our aim is to give some further characterizations of these rings over more general classes of rings, and address several questions about these rings. We obtain characterizations of max-QF rings over several classes of rings including local, semilocal right semihereditary, right non-singular right Noetherian and right non-singular right finite dimensional rings. We prove that for a ring R being right almost-QF and right max-QF are not left-right symmetric. We also show that right almost-QF and right max-QF rings are not closed under factor rings. This leads us to consider the rings all of whose factor rings are almost-QF and max-QF.
  • Article
    A Note on Variants of Euler's Φ-Function
    (Univ debrecen, inst Mathematics, 2024) Buyukasik, Engin; Goral, Haydar; Sertbas, Doga Can
    It is well-known that the sum of the firstnconsecutive integers alwaysdivides thek-th power sum of the firstnconsecutive integers whenkis odd. Motivatedby this result, in this note, we study the divisibility properties of the power sum ofpositive integers that are coprime tonand not surpassingn. First, we prove a finitenessresult for our divisibility sets using smooth numbers in short intervals. Then, we findthe exact structure of a certain divisibility set that contains the orders of these powersums and our result is of computational flavour.