The well-known notion of crossed module of groups is raised in this paper to the categorical level supported by the theory of categorical groups. We construct the cokernel of a categorical crossed module and we establish the universal property of this categorical group. We also prove a suitable 2-dimensional version of the kernelcokernel lemma for a diagram of categorical crossed modules. We th...

Homotopy categorical groups of any pointed space are defined via the fundamental groupoid of iterated loop spaces. This notion allows, paralleling the group case, to introduce the notion of K-categorical groups KiR of any ring R. We also show the existence of a fundamental categorical crossed module associated to any fibre homotopy sequence and then, K1R and K2R are characterized, respectively,...

some necessary and sufficient conditions are given for the existence of a g-positive (g-repositive) solution to adjointable operator equations $ax=c,axa^{left( astright) }=c$ and $axb=c$ over hilbert $c^{ast}$-modules, respectively. moreover, the expressions of these general g-positive (g-repositive) solutions are also derived. some of the findings of this paper extend some known results in the...

‎we call a ring $r$ right generalized semiperfect if every simple right $r$-module is an epimorphic image of a flat right $r$-module with small kernel‎, ‎that is‎, ‎every simple right $r$-module has a flat $b$-cover‎. ‎we give some properties of such rings along with examples‎. ‎we introduce flat strong covers as flat covers which are also flat $b$-covers and give characterizations of $a$-perfe...

let $mathbb{f}$ be an algebraically closed field of prime characteristic $p>2$ and $(g, [p])$ a finite-dimensional restricted lie superalgebra over $mathbb{f}$. it is showed that anyfinite-dimensional indecomposable $g$-module is a module for a finite-dimensional quotient of the universal enveloping superalgebra of $g$. these quotient superalgebras are called the generalized reduced enveloping ...

Let R be a ring, M a right R-module and (S,≤) a strictly ordered monoid. In this paper we will show that if (S,≤) is a strictly ordered monoid satisfying the condition that 0 ≤ s for all s ∈ S, then the module [[MS,≤]] of generalized power series is a uniserial right [[RS,≤]] ]]-module if and only if M is a simple right R-module and S is a chain monoid.

A simplicial group is a object in the category of groups. very nice application which polygroup given this paper. Using polygroups instead groups, we already had good results from well known properties due to Loday. Loday proved that crossed module, cat1-group, categories and whose Moore complex length one are equivalent. Loday’s idea present functor groups polygroups. We show there exist cat1-...

We prove that ifM is a compact 4-manifold provided with a handle decomposition with 1-skeleton X , and if G is a finite crossed module, then the number of crossed module morphisms from the fundamental crossed module Π2(M,X , ∗) = (π1(X , ∗), π2(M,X , ∗), ∂, ⊲) into G can be re-scaled to a manifold invariant IG (i. e. not dependent on the choice of 1-skeleton), a construction similar to David Ye...

In this paper following Conduché’s, [12], way of defining 2-crossed modules which are equivalent to Carrasco-Cegarra’s, [10], 2-hyper crossed complexes, we define the three crossed module of groups as a model for 4-types.