Let (U, R) be an approximation space with U being non-empty set and R equivalence relation on U, let $${\overline{G}}$$ $${\underline{G}}$$ the upper lower of subset G U. A topological rough group is a $$G=({\underline{G}}, {\overline{G}})$$ endowed topology, which induced from , such that product mapping $$f: G\times G\rightarrow {\overline{G}}$$ inverse are continuous. In class groups, relati...

Let G be a finite group and let K = x the conjugacy class of an element G. In this paper, it is proved that if N normal subgroup such coset union ? 1 (the inverse x), then ? ? are solvable. As application, we prove there exists natural number n ? 2 ? ,

Objectives: The goal of this paper is to introduce the ideas Contra soft generalized** (briefly g**). Continuous functions and almost g**) – in topological spaces. Additionally, we discussed some its characteristics. Methods: To obtain definition contra g**- continuous functions, used previously introduced definition(1) (i.e. inverse image every closed set FQ g**-closed FP). Also, regular open ...

In contrast to the semilattice of groups case, an inverse semigroup S which is the union of strongly ^-reflexive inverse subsemigroups need not be strongly £-reflexive. If, however, the union is saturated with respect to the Green's relation <3), and in particular if the union is a disjoint one, then 5 is indeed strongly £-reflexive. This is established by showing that fy -saturated inverse sub...

A 2-group is a ‘categorified’ version of a group, in which the underlying set G has been replaced by a category and the multiplication map m: G×G → G has been replaced by a functor. Various versions of this notion have already been explored; our goal here is to provide a detailed introduction to two, which we call ‘weak’ and ‘coherent’ 2-groups. A weak 2-group is a weak monoidal category in whi...

We present an extension, for Banach algebras, of the due to Corach et al, Jacobson’s lemma on g-Drazin inverse (Comm. Algebra, 41(2013), 520–531).

Let G be a simple, undirected graph and Gw be the positive weighted graph obtained from G by giving weights to its edges using the positive weight function w. A weighted graph Gw is said to be nonsingular if its adjacency matrix A(Gw) is nonsingular. Let G denote the class of connected, unweighted, bipartite graphs G with a unique perfect matching M such that G/M (the graph obtained by contract...