We study the structure of longest sequences in which have no zero-sum subsequence of length n (or less). We prove, among other results, that for and d arbitrary, or and d = 3, every sequence of c(n,d)(n-1) elements in which has no zero-sum subsequence of length n consists of c(n,d) distinct elements each appearing n-1 times, where and .
From a paper by A. Angelakis and P. Stevenhagen on the determination of a family of imaginary quadratic fields having isomorphic absolute Abelian Galois groups , we study any such issue for arbitrary number fields . We show that this kind of property is probably not easily generalizable, apart from imaginary quadratic fields, because of some -adic obstructions coming from the global units of . By restriction to the -Sylow subgroups of and assuming the Leopoldt conjecture we show that the...
In this paper we consider completely decomposable torsion-free groups and we determine the subgroups which are ideals in every ring over such groups.
The investigation of quantitative aspects of non-unique factorizations in the ring of integers of an algebraic number field gives rise to combinatorial problems in the class group of this number field. In this paper we investigate the combinatorial problems related to the function 𝓟(H,𝓓,M)(x), counting elements whose sets of lengths have period 𝓓, for extreme choices of 𝓓. If the class group meets certain conditions, we obtain the value of an exponent in the asymptotic formula of this function...
It is a well-known fact that modules over a commutative ring in general cannot be classified, and it is also well-known that we have to impose severe restrictions on either the ring or on the class of modules to solve this problem. One of the restrictions on the modules comes from freeness assumptions which have been intensively studied in recent decades. Two interesting, distinct but typical examples are the papers by Blass [1] and Eklof [8], both jointly with Shelah. In the first case the authors...