We compute the Fredholm index, index (DA), of the operator DA=(d/dt)+ A on L2 (R; H)
associated with the operator path {A (t)} t=−∞∞, where (Af)(t)= A (t) f (t) for ae t∈ R, and …

Mohammed Hichem Mortad ON THE CLOSEDNESS, THE SELF-ADJOINTNESS AND THE
NORMALITY OF THE PRODUCT OF TWO UNBOUNDED OPERATORS 1. In Page 1 …

STABILITY OF ALMOST CLOSED OPERATORS ON A HILBERT SPACE 1. Introduction Let us
denote by B(H) the algebra of bounded linear oper Page 1 SARAJEVO JOURNAL OF …

The purpose of this paper is to introduce some new metrics on the set C (H) of closed
densely defined operators on a Hilbert space H and we characterize the closure of the …

In this paper we give some topological conditions which ensure the closedness of the sum
and product of two closed linear operators acting in a Hilbert space. We get also a general …

In the present paper we give results on the closedness and the self-adjointness of the sum of
two unbounded operators. We present a new approach to these fundamental questions in …

The paper present a survey of results concerning the fundamental properties of the Drazin
inverse for bounded operators and an interesting study of the Drazin inverse for a closed …

Il y'a quatres ans de cela, je me suis rendu à l'université d'oran pour prendre contact avec
mon directeur de thèse, on s' est fixé l'objectif de résoudre les conditions pour lesquelles les …