A New Construction of the Injective Hull
Canadian mathematical bulletin, Tome 11 (1968) no. 1, pp. 19-21
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The definition of injectivity, and the proof that every module has an injective extension which is a subextension of every other injective extension, are due to R. Baer [B]. An independent proof using the notion of essential extension was given by Eckmann-Schopf [ES]. Both proofs require the p reliminary construction of some injective overmodule. In [F] I showed how the latter proof could be freed from this requirement by exhibiting a set F in which every essential extension could be embedded. Subsequently J. M. Maranda pointed out that F has minimal cardinality. It follows that F is equipotent with the injective hull. Below Icon struct the injective hull by equipping Fit self with a module strucure.
Fleischer, Isidore. A New Construction of the Injective Hull. Canadian mathematical bulletin, Tome 11 (1968) no. 1, pp. 19-21. doi: 10.4153/CMB-1968-002-3
@article{10_4153_CMB_1968_002_3,
author = {Fleischer, Isidore},
title = {A {New} {Construction} of the {Injective} {Hull}},
journal = {Canadian mathematical bulletin},
pages = {19--21},
year = {1968},
volume = {11},
number = {1},
doi = {10.4153/CMB-1968-002-3},
url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1968-002-3/}
}
B Baer, R., Abelian groups that are direct summands of every containing abelian group, Bull. Am. Math. Soc. 46 (1940) 800-806.10.1090/S0002-9904-1940-07306-9 Google Scholar
ES Eckmann, B. und Schopf, A., Über injektive Moduln, Arch. Math. 4 (1953) 75-78.10.1007/BF01899665 Google Scholar
F Fleischer, I., Sur le problème d'application universelle de M. Bourbaki, C.R. Acad. Sci. Paris 254 (1962) 3161-3163. Google Scholar
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