The following article is downloadable: Marco Grandis - George Janelidze,
From torsion theories to closure operators and factorization systems, Categ. Gen. Algebr. Struct. Appl., in press.
Downloadable from CGASA: http://cgasa.sbu.ac.ir/article_87116.html Abstract. Torsion theories are here extended to categories equipped with an ideal of ‘null morphisms’, or equivalently a full subcategory of ‘null objects’. Instances of this extension include closure operators viewed as generalised torsion theories in a ‘category of pairs’, and factorization systems viewed as torsion theories in a category of morphisms. The first point has essentially been treated in [15]. Regards Marco and George [For admin and other information see: http://www.mta.ca/~cat-dist/ ]