
doi: 10.1007/bf03323550
In the paper under review, a ring \(R\) is called a \(B_2\)-ring if for each 2-subset \(A\) of \(R\), \(| A^2|\leq 3\) -- that is, for each pair \(a,b\) of distinct elements of \(R\), the set \(\{a^2,b^2,ab,ba\}\) has at most 3 elements. Clearly, every commutative ring is a \(B_2\)-ring; and it is proved in [\textit{H. E. Bell} and \textit{A. A. Klein}, Arch. Math. 51, No. 6, 500-504 (1988; Zbl 0665.16021)] that every \(B_2\)-ring with 1 is commutative. The author of the paper under review gives a new proof of the previous result involving nothing more than consideration of various 2-subsets; but the proof in the previous reference is somewhat deeper. The author in the process has arrived at a new commutativity condition, called COPE property (commutativity or power-equality property). This property is that for each \(a,b\in R\), either \(ab=ba\) or there exists an integer \(n=n(a,b)>1\) for which \(a^n=b^n\). The special case in which there is a single \(n>1\) such that \(a^n=b^n\) for all noncommuting pairs \(a,b\) is called the strong COPE property. The main results are: Theorem 4. If \(R\) is any ring with COPE property, then the set of nilpotent elements of \(R\), \(N\) is an ideal and \(R/N\) is commutative. Theorem 5. Let \(R\) be a ring with 1. If \(R\) has the COPE property, then \(R\) is commutative. Theorem 6. If \(R\) is a semiprime ring with the strong COPE property, then \(R\) is commutative.
potent elements, nilpotent elements, Nil and nilpotent radicals, sets, ideals, associative rings, Generalizations of commutativity (associative rings and algebras), setwise commutativity conditions, commutativity theorems, Center, normalizer (invariant elements) (associative rings and algebras), semiprime rings
potent elements, nilpotent elements, Nil and nilpotent radicals, sets, ideals, associative rings, Generalizations of commutativity (associative rings and algebras), setwise commutativity conditions, commutativity theorems, Center, normalizer (invariant elements) (associative rings and algebras), semiprime rings
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