Theories of abelian Groups and Modules preserved under Extensions
نویسندگان
چکیده
A theory T of modules is preserved under extensions if for any submodule A of a module B, B is a model of T as soon as A and B/A are. We give a syntactic characterization of theories of modules preserved under extensions for the case of regular rings and also for the case of complete theory of abelian groups. This answers a question of U. Felgner. ∗This research was partly supported by the National Science and Engineering Council of Canada.
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