, Volume 15, Issue 5, pp 933-975,
Open Access This content is freely available online to anyone, anywhere at any time.
Date: 09 Feb 2011

Noncommutative Generalizations of Theorems of Cohen and Kaplansky


This paper investigates situations where a property of a ring can be tested on a set of “prime right ideals.” Generalizing theorems of Cohen and Kaplansky, we show that every right ideal of a ring is finitely generated (resp. principal) iff every “prime right ideal” is finitely generated (resp. principal), where the phrase “prime right ideal” can be interpreted in one of many different ways. We also use our methods to show that other properties can be tested on special sets of right ideals, such as the right artinian property and various homological properties. Applying these methods, we prove the following noncommutative generalization of a result of Kaplansky: a (left and right) noetherian ring is a principal right ideal ring iff all of its maximal right ideals are principal. A counterexample shows that the left noetherian hypothesis cannot be dropped. Finally, we compare our results to earlier generalizations of Cohen’s and Kaplansky’s theorems in the literature.

Presented by Kenneth R. Goodearl.
The author was supported in part by a Ford Foundation Predoctoral Diversity Fellowship. This work is a portion of his Ph.D. thesis at the University of California, Berkeley.