{"title":"无零范畴中态射的正规分解","authors":"Renier Jansen , Muhammad Qasim , Walter Tholen","doi":"10.1016/j.jalgebra.2025.04.016","DOIUrl":null,"url":null,"abstract":"<div><div>For a morphism <span><math><mi>f</mi><mo>:</mo><mi>A</mi><mo>→</mo><mi>B</mi></math></span> in a category <span><math><mi>C</mi></math></span> with sufficiently many finite limits and colimits, we discuss an elementary construction of a functorial decomposition<span><span><img></span></span> which, if <span><math><mi>C</mi></math></span> happens to have a zero object, amounts to the standard decomposition<span><span><img></span></span> In this way we obtain natural notions of normal monomorphism and normal epimorphism also in non-pointed categories, as special types of regular mono- and epimorphisms. We examine the factorization behaviour of these classes of morphisms in general, compare the generalized normal decompositions with other types of threefold factorizations, and illustrate them in some every-day categories. The concrete construction of normal decompositions in the slices or coslices of some of these categories can be challenging. Amongst many others, in this regard we consider particularly the categories of T<sub>1</sub>-spaces and of groups.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"678 ","pages":"Pages 392-425"},"PeriodicalIF":0.8000,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"The normal decomposition of a morphism in categories without zeros\",\"authors\":\"Renier Jansen , Muhammad Qasim , Walter Tholen\",\"doi\":\"10.1016/j.jalgebra.2025.04.016\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>For a morphism <span><math><mi>f</mi><mo>:</mo><mi>A</mi><mo>→</mo><mi>B</mi></math></span> in a category <span><math><mi>C</mi></math></span> with sufficiently many finite limits and colimits, we discuss an elementary construction of a functorial decomposition<span><span><img></span></span> which, if <span><math><mi>C</mi></math></span> happens to have a zero object, amounts to the standard decomposition<span><span><img></span></span> In this way we obtain natural notions of normal monomorphism and normal epimorphism also in non-pointed categories, as special types of regular mono- and epimorphisms. We examine the factorization behaviour of these classes of morphisms in general, compare the generalized normal decompositions with other types of threefold factorizations, and illustrate them in some every-day categories. The concrete construction of normal decompositions in the slices or coslices of some of these categories can be challenging. Amongst many others, in this regard we consider particularly the categories of T<sub>1</sub>-spaces and of groups.</div></div>\",\"PeriodicalId\":14888,\"journal\":{\"name\":\"Journal of Algebra\",\"volume\":\"678 \",\"pages\":\"Pages 392-425\"},\"PeriodicalIF\":0.8000,\"publicationDate\":\"2025-04-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Algebra\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0021869325002273\",\"RegionNum\":2,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Algebra","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0021869325002273","RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
The normal decomposition of a morphism in categories without zeros
For a morphism in a category with sufficiently many finite limits and colimits, we discuss an elementary construction of a functorial decomposition which, if happens to have a zero object, amounts to the standard decomposition In this way we obtain natural notions of normal monomorphism and normal epimorphism also in non-pointed categories, as special types of regular mono- and epimorphisms. We examine the factorization behaviour of these classes of morphisms in general, compare the generalized normal decompositions with other types of threefold factorizations, and illustrate them in some every-day categories. The concrete construction of normal decompositions in the slices or coslices of some of these categories can be challenging. Amongst many others, in this regard we consider particularly the categories of T1-spaces and of groups.
期刊介绍:
The Journal of Algebra is a leading international journal and publishes papers that demonstrate high quality research results in algebra and related computational aspects. Only the very best and most interesting papers are to be considered for publication in the journal. With this in mind, it is important that the contribution offer a substantial result that will have a lasting effect upon the field. The journal also seeks work that presents innovative techniques that offer promising results for future research.