L. Bican, KA MFF UK, Sokolovska 83, 186 75 Praha 8, Czech Republic, e-mail: bican@karlin.mff.cuni.cz; B. Torrecillas, Department of Algebra and Analysis, Universidad de Almeria, 04071 Almeria, Spain, e-mail: btorreci@ual.es
Abstract: Let $\Cal G$ be an abstract class (closed under isomorpic copies) of left $R$-modules. In the first part of the paper some sufficient conditions under which $\Cal G$ is a precover class are given. The next section studies the $\Cal G$-precovers which are $\Cal G$-covers. In the final part the results obtained are applied to the hereditary torsion theories on the category on left $R$-modules. Especially, several sufficient conditions for the existence of $\sigma$-torsionfree and $\sigma$-torsionfree $\sigma$-injective covers are presented.
Keywords: precover, cover, (pre)cover class of modules, hereditary torsion theory, relatively injective modules
Classification (MSC 2000): 16D90, 16S90, 16D50
Full text available as PDF (smallest), as compressed PostScript (.ps.gz) or as raw PostScript (.ps).
Access to the full text of journal articles on this site is restricted to the subscribers of Myris Trade.
To activate your access, please contact Myris Trade at myris@myris.cz.
Subscribers of Springer (formerly Kluwer) need to access the articles on their site, which is http://www.springeronline.com/10587.
