A note on S-flat preenvelopes
摘要
We investigate the notion of S-flat preenvelopes of modules. In particular, we give an example that a ring R being coherent does not imply that every R-module has an S-flat preenvelope, giving a negative answer to the question proposed by D. Bennis and A. Bouziri (2025). Besides, we also show that a ring RS being coherent also does not imply that R is an S-coherent ring in general.