Rational Functions Invariant under a Finite Abelian Group.
A submodule of a -primary module of bounded order is known to be regular if and have simultaneous bases. In this paper we derive necessary and sufficient conditions for regularity of a submodule.
We generalize the notion of a coarse sequential convergence compatible with an algebraic structure to a coarse one in a given class of convergences. In particular, we investigate coarseness in the class of all compatible convergences (with unique limits) the restriction of which to a given subset is fixed. We characterize such convergences and study relative coarseness in connection with extensions and completions of groups and rings. E.g., we show that: (i) each relatively coarse dense group precompletion...
Let be a finite and nontrivial abelian group with . A conjecture of Hamidoune says that if is a sequence of integers, all but at most one relatively prime to , and is a sequence over with , the maximum multiplicity of at most , and , then there exists a nontrivial subgroup such that every element can be represented as a weighted subsequence sum of the form , with a subsequence of . We give two examples showing this does not hold in general, and characterize the counterexamples...
We present a system of interrelated conjectures which can be considered as restricted addition counterparts of classical theorems due to Kneser, Kemperman, and Scherk. Connections with the theorem of Cauchy-Davenport, conjecture of Erdős-Heilbronn, and polynomial method of Alon-Nathanson-Ruzsa are discussed.The paper assumes no expertise from the reader and can serve as an introduction to the subject.