From a single chain to a large family of submodules.
Fully inert submodules of torsion-free -modules are investigated. It is proved that if the module considered is either free or complete, these submodules are exactly those which are commensurable with fully invariant submodules; examples are given of torsion-free -modules for which this property fails.
In this paper, we present a considerable simplification of the proof of a theorem by Gan and Knox, stating a sufficient and necessary condition for existence of a composition of two formal power series. Then, we consider the behavior of such series and their (formal) derivatives at the boundary of the convergence circle, obtaining in particular a theorem of Bugajewski and Gan concerning the structure of the set of points where a formal power series is convergent with all its derivatives.
We describe a correspondence between -invariant tensors and graphs. We then show how this correspondence accommodates various types of symmetries and orientations.
Let be a group with identity and let be a -graded ring. In this paper, we introduce and study the concept of graded -ideals of . A proper graded ideal of is called a graded -ideal of if whenever where , then either or or . We introduce several results concerning --ideals. For example, we give a characterization of graded -ideals and their homogeneous components. Also, the relations between graded -ideals and others that already exist, namely, the graded prime ideals,...