ON RELATIVE FLATNESS

Abstract

For a torsion radical, δ, we study various types of relative flatness and regularity. We obtain conditions valid when every R-module is δ-flat, when every R-module is semi-δ-flat and when every R-module is semi-δ-injective, and hence we characterize quasi-Frobenius rings R together with any torsion radical, δ, on R-mod. We define a ring to be δ perfect whenever every δ-flat module is projective and obtain extensions of some known results on perfect rings. We also introduce a relative form of the Jacobson Radical defined in terms of δ-flatness.