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A simple ring over which proper cyclics are continuous is a PCI-ring. (English) Zbl 0916.16003

Rings over which proper cyclics are injective (called PCI-rings) have been characterized by C. Faith [Pac. J. Math. 45, 97-112 (1973; Zbl 0258.16024)] and R. F. Damiano [Proc. Am. Math. Soc. 77, 11-14 (1979; Zbl 0425.16022)] as semisimple artinian rings or simple right noetherian, right hereditary domains over which each proper cyclic module is semisimple. Dinh Van Huynh, S. K. Jain and S. R. López-Permouth [J. Algebra 184, No. 2, 789-794 (1996; 856.16020)] showed that simple rings over which proper cyclics are quasi-injective (called PCQI-rings) are the same as simple PCI-rings. The authors extend the result by showing that a simple ring over which proper cyclics are continuous is indeed a PCI-ring. The proof has a strong computational flavor, as it is based on looking at the form of the cyclic modules involved and on the precise computation of the intersection of certain pairs of modules.

MSC:

16D60 Simple and semisimple modules, primitive rings and ideals in associative algebras
16D50 Injective modules, self-injective associative rings
16D70 Structure and classification for modules, bimodules and ideals (except as in 16Gxx), direct sum decomposition and cancellation in associative algebras)
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