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 ≠ R and X is a free right R-module then the right R-module Q ⊕ X is semi-projective if and only if there does not exist an R-epimorphism from X to Q.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-cm127-1-5,
author = {Derya Keskin T\"ut\"unc\"u and Berke Kalebo\u gaz and Patrick F. Smith},
title = {Direct sums of semi-projective modules},
journal = {Colloquium Mathematicae},
volume = {126},
year = {2012},
pages = {67-81},
zbl = {1260.16002},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm127-1-5}
}
Derya Keskin Tütüncü; Berke Kaleboğaz; Patrick F. Smith. Direct sums of semi-projective modules. Colloquium Mathematicae, Tome 126 (2012) pp. 67-81. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm127-1-5/