A ring $R$ is called semiperfect if every finitely generated $R$module has a projective cover, and it can be proved that this is equivalent to say that the category consisting of the finitely generated projective $R$modules is KrullSchmidt. I was wondering, and what about the rings $R$ such that every finitely presented $R$module has a projective cover? Do these rings have a special name, and are there characterizations of these rings, just like there are for semiperfect rings?
1 Answer
Such rings were called "$F$semiperfect", and more recently (thanks to rschweib for the information) "semiregular".
One characterization is that these are the rings $R$ such that $\bar{R}=R/J(R)$, the quotient by the Jacobson radical, is von Neumann regular and idempotents lift from $\bar{R}$ to $R$. This is analogous to the characterization of semiperfect rings as those for which $\bar{R}$ is semisimple and idempotents lift from $\bar{R}$ to $R$.
Some old references:
Oberst, Ulrich; Schneider, HansJürgen, Die Struktur von projektiven Moduln. (The structure of projective modules.), Invent. Math. 13, 295304 (1971). ZBL0232.16020.
Azumaya, Goro, Fsemiperfect modules, J. Algebra 136, No. 1, 7385 (1991). ZBL0717.16005.

3$\begingroup$ I think one will find through a google search that the more common name for what you are calling an "Fsemiperfect ring" nowadays is "semiregular ring." $\endgroup$– rschwiebNov 5, 2020 at 14:05

1$\begingroup$ @rschwieb Thanks, I didn't know that! The only reason I knew where to look at all was that I had some reason (that I've now forgotten) to look at Azumaya's paper many years ago. $\endgroup$ Nov 5, 2020 at 14:09

1$\begingroup$ cambridge.org/core/services/aopcambridgecore/content/view/… seems a good reference $\endgroup$ Nov 5, 2020 at 17:12

1$\begingroup$ Semiregular rings show up quite a bit in the study of exchange rings. $\endgroup$ Nov 5, 2020 at 18:12