Direct sums of semi-projective modules
Volume 127 / 2012
Colloquium Mathematicum 127 (2012), 67-81
MSC: Primary 16D40, 16U10; Secondary 16D50, 13C11, 13F10.
DOI: 10.4064/cm127-1-5
Abstract
We investigate when the direct sum of semi-projective modules is semi-projective. It is proved that if $R$ is a right Ore domain with right quotient division ring $Q \not =R$ and $X$ is a free right $R$-module then the right $R$-module $Q \oplus X$ is semi-projective if and only if there does not exist an $R$-epimorphism from $X$ to $Q$.
