{"title":"Index Sets of Decidably Categorical Models that are Elementarily Equivalent to the Powers of Omega","authors":"N. A. Bazhenov, M. V. Zubkov, M. I. Marchuk","doi":"10.1007/s10469-026-09842-4","DOIUrl":null,"url":null,"abstract":"<p>A strongly constructivizable model S is decidably categorical if for any decidable copies A and B of S, there exists a computable isomorphism from A onto B. The paper investigates the complexity of families of decidably categorical models belonging to familiar finitely axiomatizable classes. For a non-zero natural number n, the index set of decidably categorical linear orders elementarily equivalent to the ordinal <i>ω</i><sup><i>n</i></sup> is an m-complete <span>\\({\\Sigma}_{2\\text{n}+2}^{0}\\)</span>-set. The index set of decidably categorical structures which are elementarily equivalent to <i>ω</i><sup><i>n</i></sup>, enriched by the successor relation, is an m-complete <span>\\({\\Sigma}_{2\\text{n}+1}^{0}\\)</span>-set.</p>","PeriodicalId":7422,"journal":{"name":"Algebra and Logic","volume":"64 6","pages":"397 - 401"},"PeriodicalIF":0.4000,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Algebra and Logic","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1007/s10469-026-09842-4","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"LOGIC","Score":null,"Total":0}
引用次数: 0
Abstract
A strongly constructivizable model S is decidably categorical if for any decidable copies A and B of S, there exists a computable isomorphism from A onto B. The paper investigates the complexity of families of decidably categorical models belonging to familiar finitely axiomatizable classes. For a non-zero natural number n, the index set of decidably categorical linear orders elementarily equivalent to the ordinal ωn is an m-complete \({\Sigma}_{2\text{n}+2}^{0}\)-set. The index set of decidably categorical structures which are elementarily equivalent to ωn, enriched by the successor relation, is an m-complete \({\Sigma}_{2\text{n}+1}^{0}\)-set.
期刊介绍:
This bimonthly journal publishes results of the latest research in the areas of modern general algebra and of logic considered primarily from an algebraic viewpoint. The algebraic papers, constituting the major part of the contents, are concerned with studies in such fields as ordered, almost torsion-free, nilpotent, and metabelian groups; isomorphism rings; Lie algebras; Frattini subgroups; and clusters of algebras. In the area of logic, the periodical covers such topics as hierarchical sets, logical automata, and recursive functions.
Algebra and Logic is a translation of ALGEBRA I LOGIKA, a publication of the Siberian Fund for Algebra and Logic and the Institute of Mathematics of the Siberian Branch of the Russian Academy of Sciences.
All articles are peer-reviewed.