Covering abelian groups with cyclic subsets.
Let be a Krull monoid with finite class group where every class contains some prime divisor. It is known that every set of lengths is an almost arithmetical multiprogression. We investigate which integers occur as differences of these progressions. In particular, we obtain upper bounds for the size of these differences. Then, we apply these results to show that, apart from one known exception, two elementary -groups have the same system of sets of lengths if and only if they are isomorphic.
A group has the endomorphism kernel property (EKP) if every congruence relation on is the kernel of an endomorphism on . In this note we show that all finite abelian groups have EKP and we show infinite series of finite non-abelian groups which have EKP.
In this short note a correct proof of Theorem 3.3 from [Tărnăuceanu M., Solitary quotients of finite groups, Cent. Eur. J. Math., 2012, 10(2), 740–747] is given.
It is a known result that if a finite abelian group of odd order is a direct product of lacunary cyclic subsets, then at least one of the factors must be a subgroup. The paper gives an elementary proof that does not rely on characters.
There are four resolvable Steiner triple systems on fifteen elements. Some generalizations of these systems are presented here.