On classification of pomonoids by properties of generators

In this paper, we attempt to collect the knowledge on generators in the category Pos-[Formula: see text] and to apply this to proceed on the questions of homological classification of ordered monoids, that is results of the type: all generators in the category Pos-[Formula: see text], have a flatness property if and only if [Formula: see text] has a certain property.

On homological classification of pomonoids by GP-po-flatness of S-posets

In this paper, we introduce GP-po-flatness property of S-posets over a pomonoid S, which lies strictly between principal weak po-flatness and po-torsion freeness. Furthermore, we investigate the homological classification problems of pomonoids by using this new property. Finally, we consider direct products of GP-po-flat S-posets. As an application, characterizations of pomonoids over which direct products of nonempty families of principally weakly po-flat S-posets are principally weakly po-flat are obtained, and some results of Khosravi, R. in a certain extent are generalized.

On projective covers of semimodules and perfect semirings

We consider two natural concepts of "perfectness" in a semiring context: the perfectness in terms of projective covers, and the perfectness in Bass's sense. For both cases we show that the class of right (left) perfect semirings coincides with the class of right (left) perfect rings; in particular, we completely confirm Conjecture of [Y. Katsov, Toward homological classification of semirings: Serre's conjecture and Bass's perfectness in a semiring context. Algebra Universalis52 (2004) 197–214].