Rings of Clean Index 4 and Applications

摘要

This article is a continuation of the work in [3] on clean index of rings. Motivated by recent work [5] on uniquely clean rings, the clean index of a ring was introduced in [3] to study the structure of rings, where arbitrary rings of clean indices 1, 2, and 3, respectively, are characterized. In particular, clean rings of clean indices 1, 2, and 3 are determined. In this article, we characterize the rings of clean index 4. As applications, clean rings of clean indices 4, 5, 6 and 7 are completely determined.