Additive Property of Drazin Invertibility of Elements

In this article, we investigate additive properties of the Drazin inverse of elements in rings and algebras over an arbitrary field. Under the weakly commutative condition of $ab = \lambda ba$, we show that $a-b$ is Drazin invertible if and only if $aa^{D}(a-b)bb^{D}$ is Drazin invertible. Next, we give explicit representations of $(a+b)^{D}$, as a function of $a, b, a^{D}$ and $b^{D}$, under the conditions $a^{3}b = ba$ and $b^{3}a = ab$.Comment: 17 page

A new class of partial orders

Let $R$ be a unital $*$-ring. For any $a,w,b\in R$, we apply the defined $w$-core inverse to define a new class of partial orders in $R$, called the $w$-core partial order. Suppose $a,b\in R$ are $w$-core invertible. We say that $a$ is below $b$ under the $w$-core partial order, denoted by $a\overset{\tiny{\textcircled{\#}}}\leq_w b$, if $a_w^{\tiny{\textcircled{\#}}} a=a_w^{\tiny{\textcircled{\#}}} b$ and $awa_w^{\tiny{\textcircled{\#}}} =bwa_w^{\tiny{\textcircled{\#}}}$, where $a_w^{\tiny{\textcircled{\#}}}$ denotes the $w$-core inverse of $a$. Characterizations of the $w$-core partial order are given. Also, the relationships with several types of partial orders are considered. In particular, we show that the core partial order coincides with the $a$-core partial order, and the star partial order coincides with the $a^*$-core partial order

A note on clean elements and inverses along an element

Let R be an associative ring with unity 1 and let a, d is an element of R. An element a is an element of R is called invertible along d if there exists unique a(parallel to d) such that a(parallel to d) ad = d = daa(parallel to d) and a(parallel to d )is an element of dR boolean AND Rd (see [6, Definition 4]). In this note, we present new characterizations for the existence of a(parallel to d )by clean decompositions of ad and da. As applications, existence criteria for the Drazin inverse and the group inverse are given.The authors are highly grateful to the referee for his/her valuable comments and suggestions which greatly improved this paper. This research is supported by the National Natural Science Foundation of China (No. 11801124), the Fundamental Research Funds for the Central Universities (No. JZ2018HGTB0233) and the Natural Science Foundation of Anhui Province (No. 1808085QA16), and the Portuguese Funds through FCT-'Fundacao para a Ciencia e a Tecnologia', within the project UID-MAT-00013/2013

The Moore-Penrose inverse of differences and products of projectors in a ring with involution

In this paper, we study the Moore–Penrose inverses of differences and products of projectors in a ring with involution. Some necessary and sufficient conditions for the existence of the Moore–Penrose inverse are given. Moreover, the expressions of the Moore–Penrose inverses of differences and products of projectors are presented.Portuguese Funds through FCT - ‘Fundação para a Ciência e Tecnologia’, within the project PEst-OE/MAT/UI0013/2014.info:eu-repo/semantics/publishedVersio