UBC Theses and Dissertations
Local radical and semi-simple classes of rings Stewart, Patrick Noble
For any cardinal number K ≥2 and any non-empty class of rings ℛ we make the following definitions. The class ℛ(K) is the class of all rings R such that every subring of R which is generated by a set of cardinality strictly less than K is in ℛ . The class ℛg(K) is the class of all rings R such that every non-zero homomorphic image of R contains a non-zero subring in ℛ which is generated by a set of cardinality strictly less than K . Several properties of the classes ℛg(K) and ℛ(K) are determined. In particular, conditions are specified which imply that ℛ(K) is a radical class or a semi-simple class. Necessary and sufficient conditions that the class ℑ of all ℛg(K) semi-simple rings be equal to ℑ(K) are given. The classes ℛ(K) and ℛg(K) when K = 2 or K = (formula omitted)₀ are considered in detail for various classesℛ (including the cases when ℛ is one of the well-known radical classes). In all cases when ℛ is one of the well-known radical classes it Is shown that ℛ(2) and ℛ(formula omitted) are radical classes and whenever they contain all nilpotent rings they are shown to be special radical classes. Those radical classes ℛ(2) which are contained in FC (R € FC if and only if for all x € R , x is torsion) are characterized. Let ℛ be any radical class. The largest radical class (formula omitted) (if one exists) such that (formula omitted)(R) Ո ℛ(R) = (0) for all rings R is defined to be the local complement of ℛ̅̅ and is denoted by ℛ. If ℛ = ℛ(formula omitted) then the local complement ℛ exists and ℛ= ℛ(2) . The local complements of all radicals discussed are determined. We are able to apply some of these results in order to classify those classes of rings which are both semi-simple and radical classes.
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