@article{Al-janabi_2020, title={Some Properties of D-Operator on Hilbert Space}, volume={61}, url={https://ijs.uobaghdad.edu.iq/index.php/eijs/article/view/2814}, DOI={10.24996/ijs.2020.61.12.24}, abstractNote={<p>In this paper, we introduce a new type of Drazin invertible operator on Hilbert spaces, which is called D-operator. Then, some properties of the class of D-operators are studied. We prove that the D-operator preserves the scalar product, the unitary equivalent property, the product and sum of two D-operators are not D-operator in general but the direct product and tenser product is also D-operator.</p>}, number={12}, journal={Iraqi Journal of Science}, author={Al-janabi, Eiman}, year={2020}, month={Dec.}, pages={3366-3371} }