{"title":"Central reflections and nilpotency in exact Mal’tsev categories","authors":"Clemens Berger, Dominique Bourn","doi":"10.1007/s40062-016-0165-8","DOIUrl":null,"url":null,"abstract":"<p>We study nilpotency in the context of exact Mal’tsev categories taking central extensions as the primitive notion. This yields a nilpotency tower which is analysed from the perspective of Goodwillie’s functor calculus. We show in particular that the reflection into the subcategory of <i>n</i>-nilpotent objects is the universal endofunctor of degree <i>n</i> if and only if every <i>n</i>-nilpotent object is <i>n</i>-folded. In the special context of a semi-abelian category, an object is <i>n</i>-folded precisely when its Higgins commutator of length <span>\\(n+1\\)</span> vanishes.</p>","PeriodicalId":636,"journal":{"name":"Journal of Homotopy and Related Structures","volume":"12 4","pages":"765 - 835"},"PeriodicalIF":0.5000,"publicationDate":"2016-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s40062-016-0165-8","citationCount":"10","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Homotopy and Related Structures","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1007/s40062-016-0165-8","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 10
Abstract
We study nilpotency in the context of exact Mal’tsev categories taking central extensions as the primitive notion. This yields a nilpotency tower which is analysed from the perspective of Goodwillie’s functor calculus. We show in particular that the reflection into the subcategory of n-nilpotent objects is the universal endofunctor of degree n if and only if every n-nilpotent object is n-folded. In the special context of a semi-abelian category, an object is n-folded precisely when its Higgins commutator of length \(n+1\) vanishes.
期刊介绍:
Journal of Homotopy and Related Structures (JHRS) is a fully refereed international journal dealing with homotopy and related structures of mathematical and physical sciences.
Journal of Homotopy and Related Structures is intended to publish papers on
Homotopy in the broad sense and its related areas like Homological and homotopical algebra, K-theory, topology of manifolds, geometric and categorical structures, homology theories, topological groups and algebras, stable homotopy theory, group actions, algebraic varieties, category theory, cobordism theory, controlled topology, noncommutative geometry, motivic cohomology, differential topology, algebraic geometry.