A classical problem in the literature seeks minimal number of proper subgroups whose union is a given finite group. different question, with applications to error-correcting codes and graph colorings, involves covering vector spaces over fields by (minimally many) subspaces. In this note we cover $R$-modules submodules for commutative rings $R$, thereby subsuming recovering both cases above. Sp...

A module M is called ?-?ss-supplemented if every submodule X of has a ?ss-supplement Y in which direct summand such that + = and ? Soc? (Y) where Soc?(Y) the sum simple ?-small submodules Y? for some M. Moreover, completely ?-?ss-supplemented. Thus, we present two new types algebraic structures are stronger than ?-D11 ?-D+11-modules, respectively. In this paper investigate basic properties, dec...

Let $R$ be a commutative ring and let $I$ be an ideal of $R$. In this paper, we will introduce the notions of 2-absorbing $I$-prime and 2-absorbing $I$-second submodules of an $R$-module $M$ as a generalization of 2-absorbing and strongly 2-absorbing second submodules of $M$ and explore some basic properties of these classes of modules.

In this paper we investigate decompositions of submodules in modules over a Proufer domain into intersections of quasi-primary and classical quasi-primary submodules. In particular, existence and uniqueness of quasi-primary decompositions in modules over a Proufer domain of finite character are proved. Proufer domain; primary submodule; quasi-primary submodule; classical quasi-primary; decompo...

Let $G$ be a group with identity $e$. $R$ $G$-graded commutative ring, $M$ graded $R$-module and $A\subseteq h(R)$ multiplicatively closed subset of $R$. In this paper, we introduce the concept $A$-2-absorbing submodules as generalization 2-absorbing $A$-prime $M.$ We investigate some properties class submodules.

Subsingular vectors of the N=2 superconformal algebras were discovered, and examples given, in 1996. Shortly afterwards Semikhatov and Tipunin claimed to have obtained a complete classification of the N=2 subsingular vectors in the paper ‘The Structure of Verma Modules over the N=2 Superconformal algebra’, hep-th/9704111, published in CMP 195 (1998) 129. Surprisingly, the only explicit examples...