Abstract
We introduce the concepts of (n, d)-injective and (n, d)-flat as generalizations of injective, flat modules and homological dimensions, and use them to characterize right n-coherent rings and right (weak) (n, d)-rings in various way. Some known results can be obtained as corollaries.
Acknowledgments
The author wishes to thank Professors Wenting Tong and Weimin Xue for many valuable communications, and the referee for several helpful suggestions. This research is supported by the National Science Foundation of China (A0324656).
Notes
#Communicated by R. Wisbauer.