Let ■ be a pre-additive category. Assume that ψ:X→X is a morphism of (?). In this paper, we give the necessary and sufficient conditions for ψ to have the Drazin inverse by using the von Neumann regular inverse for the ψk, and extend a result by Puystjens and Hartwig from the group inverse to Drazin inverse.
A ring R is called right zip provided that if the annihilator r_R(X) of a subset X of R is zero,then r_R(Y)=0 for some finite subset Y■X.Such rings have been studied in literature.For a right R-module M,we introduce the notion of a zip module,which is a generalization of the right zip ring.A number of properties of this sort of modules are established,and the equivalent conditions of the right zip ring R are given.Moreover,the zip properties of matrices and polynomials over a module M are studied.
本文主要给出F-复盖的直积还是一个F-复盖的充分条件和充要条件.假设右R-模类F在直积,直和项下封闭,{M_i}i∈I是一簇右R-模.如果每个φ_i:F_i→M_i都是M_i的具有唯一映射性质的F-复盖,且multiply from i∈I M_i有F-复盖,则可以得到是multiply from i∈I M_i的F-复盖.另外我们证明如果φ_i:F_i→M_i是M_i的F-复盖,且multiply from i∈I M_i有F-复盖,则是multiply from i∈I M_iF-复盖当且仅当multiply from i∈I Kerφ~i不包含multiply from i∈I F_i中的非零直和项.从而改进、推广了文[6]中的相应结果.
