1. Let R be a ring with unity. An R-module M is said to be balanced or to have the double centralizer property, if the natural homomorphism from R to the double centralizer of M is surjective. If all left and right K-modules are balanced, R is called balanced. It is well known that every artinian uniserial ring is balanced. In [5], J. P. Jans conjectured that those were the only (artinian) bala...

Let S be a finitely generated standard multigraded algebra over an Artinian local ring A; M a finitely generated multigraded S-module. This paper answers to the question when mixed multiplicities of M are positive and characterizes them in terms of lengths of A-modules. As an application, we get interesting results on mixed multiplicities of ideals, and recover some early results in [Te] and [TV].

Given a direct sum G of cyclic groups, we find a sharp bound for the minimal number of proper subgroups whose union is G. This problem generalizes to sums of cyclic modules over more general rings, such as local and Artinian rings or Dedekind domains and reduces to covering vector spaces by proper subspaces. As a consequence, we are also able to solve the analogous problem for monoids.

Let M be an infinite unitary module over a commutative ring R with identity. Then M is called a Jónsson module provided every proper submodule of M has smaller cardinality than M. These modules have been studied by several algebraists, including Robert Gilmer, Bill Heinzer, and the author. In this note, we recall the major results on Jónsson modules to bring the reader up to speed on current re...

We find a bound for the Goldie dimension of hereditary modules in terms of the cardinality of the generator sets of its quasi-injective hull. Several consequences are deduced. In particular, it is shown that every right hereditary module with countably generated quasi-injective hull is noetherian. Or that every right hereditary ring with finitely generated injective hull is artinian, thus answe...

We develop the theory of coregular sequences and codepth for modules that need not be finitely generated or artinian over a Noetherian ring. use this to give new version theorem Hellus characterizing set-theoretic complete intersections in terms local cohomology modules. also define quasi-cyclic as increasing unions cyclic modules, show at least two are quasi-cyclic. then focus our attention on...