循环纯phantom态射

2024-05-15 17:43魏敏敏赵仁育
吉林大学学报(理学版) 2024年2期
关键词:内射模同态范畴

魏敏敏 赵仁育

摘要: 通过引入循环纯phantom态射的概念, 给出循环纯phantom态射的一些等价刻画, 证明每个R-模都有核为循环纯内射模的满的循环纯phantom覆盖, 并讨论循环纯phantom预覆盖在环变换下的传递性.

关键词: 循环纯; 循环纯phantom态射; 预覆盖

中图分类号: O153.3文献标志码: A文章编号: 1671-5489(2024)02-0249-07

Cyclic Pure Phantom Morphisms

WEI Minmin, ZHAO Renyu

(College of Mathematics and Statistics, Northwest Normal University, Lanzhou 730070, China)

Abstract: By introducing the notion of cyclic pure phantom morphisms, we gave  some equivalent characterizations of cyclic pure phantom morphisms,  proved that every R-module had an epic cyclic pure phantom cover with the kernel cyclic pure injective modules, and discussed the transitivity of cyclic pure phantom precover under change of rings.

Keywords: cyclic pure; cyclic pure phantom morphism; precover

Phantom態射起源于拓扑学中关于CW-复形间的态射研究. 文献[1]在三角范畴中引入了phantom态射的概念, 文献[2-5]将phantom态射理论推广到了有限群环的稳定模范畴中; 文献[6]将phantom态射的概念拓展到任意结合环R上的R-模范畴中. 如果对每个(有限表示)左R-模A, Abel群同态Tor1(f,A): Tor1(M,A)→Tor1(N,A)是零同态, 则一个右R-模同态f: M→N称为phantom态射. Phantom态射可视为是平坦模的态射, 由于其在理想逼近理论[7]中具有重要作用, 因此近年来得到广泛关注[8-12].

Phantom态射与纯性有密切的关系. 作为纯性的推广, 文献[13]引入了循环纯的概念; 文献[14-15]研究了循环纯内射模和循环纯投射模; 文献[16]研究了循环纯平坦模. 受上述研究结果的启发, 本文引入并研究循环纯phantom态射.

1 预备知识

本文中R是有单位元的结合环, 所涉及的模均为酉模. 用Mod-R表示右R-模范畴. 将HomR(M,N)和MRN分别简记为Hom(M,N)和MN; 将Ext1R(M,N)和TorR1(M,N)分别简记为Ext1(M,N)和Tor1(M,N). 用Mor-R表示所有右R-模同态的范畴, 即其中的对象是所有的右R-同态f: M→N, 对象f: M1→N1到对象g: M2→N2的态射是一对右R-同态(α1,α2), 使得下图可交换:

如果P1和P2是投射右R-模且P是可裂单态射, 则Mor-R中的对象P: P1→P2称为投射对象. 对偶地, 如果E1和E2是内射右R-模且E是可裂满态射, 则Mor-R中的对象E: E1→E2称为内射对象[9,17].

参考文献

[1]NEEMAN A. The Brown Representability Theorem and Phantomless Triangulated Categories [J]. Journal of Algebra, 1992, 151(1): 118-155.

[2]BENSON D J. Phantom Maps and Purity in Modular Representation Theory. Ⅲ [J]. Journal of Algebra, 2002, 248(2): 747-754.

[3]BENSON D J, GNACADJA G P. Phantom Maps and Purity in Modular Representation Theory. Ⅰ [J]. Fundamenta Mathematicae, 1999, 162(1/2): 37-91.

[4]BENSON D J, GNACADJA G P. Phantom Maps and Purity in Modular Representation Theory. Ⅱ [J]. Algebras and Representation Theory, 2001, 4(4): 395-404.

[5]GNACADJA G P. Phantom Maps in the Stable Module Category [J]. Journal of Algebra, 1998, 201(2): 686-702.

[6]HERZOG I. The Phantom Cover of a Module [J]. Advances in Mathematics, 2007, 215(1): 220-249.

[7]FU X H, GUIL ASENSIO P A, HERZOG I, et al. Ideal Approximation Theory [J]. Advances in Mathematics, 2013, 244: 750-790.

[8]MAO L X. Precovers and Preenvelopes by Phantom and Ext-Phantom Morphisms [J]. Communications in Algebra, 2016, 44(4): 1704-1721.

[9]MAO L X. RD-Phantom and RD-Ext-Phantom Morphisms [J]. Filomat, 2018, 32(8): 2883-2895.

[10]MAO L X. Neat-Phantom and Clean-Cophantom Morphisms [J]. Journal of Algebra and Its Applications, 2021, 20(9): 2150172-1-2150172-24.

[11]MAO L X. Higher Phantom Morphisms with Respect to a Subfunctor of Ext [J]. Algebras and Representation Theory, 2019, 22(2): 407-424.

[12]張春霞, 唐强玲. (n,d)-phantom与(n,d)-Ext-phantom态射 [J]. 山东大学学报(理学版), 2023, 58(2): 79-87. (ZHANG C X, TANG Q L. On (n,d)-Phantom and (n,d)-Ext-Phantom Morphisms [J]. Journal of Shandong University (Natural Science), 2023, 58(2): 79-87.)

[13]HOCHSTER M. Cyclic Purity versus Purity in Excellent Noetherian Rings [J]. Transactions of the American Mathematical Society, 1977, 231(2): 463-488.

[14]DIVAANI-AAZAR K, ESMKHANI M A, TOUSI M. A Criterion for Rings Which Are Locally Valuation Rings [J]. Colloquium Mathematicum, 2009, 116(2): 153-164.

[15]DIVAANI-AAZAR K, ESMKHANI M A, TOUSI M. Some Criteria of Cyclically Pure Injective Modules [J]. Journal of Algebra, 2006, 304(1): 367-381.

[16]MAO L X. Modules with Respect to Cyclic Purity [J]. Mathematica Scandinavica, 2011, 108(2): 177-197.

[17]ESTRADA S, GUIL ASENSIO P A, OZBEK F. Covering Ideals of Morphisms and Module Representations of the Quiver A2[J]. Journal of Pure and Applied Algebra, 2014, 218(10): 1953-1963.

[18]ENOEHS E E, OYONARTE L. Covers, Envelopes and Cotorsion Theories [M]. New York: Nova Science Publishers, 2002: 1-113.

[19]CRIVEI S, PREST M, TORRECILLAS B. Covers in Finitely Accessible Categories [J]. Proceedings of the American Mathematical Society, 2010, 138(4): 1213-1221.

[20]ROTMAN J J. An Introduction to Homological Algebra [M]. New York: Academic Press, 1979: 1-376.

[21]XUE W M. On Almost Excellent Extensions [J]. Algebra Colloquium, 1996, 3(2): 125-134.

(责任编辑: 赵立芹)

收稿日期: 2023-06-12.

第一作者简介: 魏敏敏(1999—), 女, 汉族, 硕士研究生, 从事环的同调理论的研究, E-mail: 18419376042@163.com.

通信作者简介: 赵仁育(1977—), 男, 汉族, 博士, 教授, 从事环的同调理论的研究, E-mail: zhaory@nwnu.edu.cn.

基金项目: 国家自然科学基金(批准号: 11861055; 12061061).

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