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1. 

   A note on partial-A-isometries and some applications

   Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Mohamed Amine Aouichaoui --- Institute of Preparatory Studies in Engineering of Monastir Tunisia, University of Monastir, Tunisia

   In this paper, the concepts of partial isometry and A-isometry are generalized. The inspiration for our investigation comes from [4, 10, 20, 27, 28, 29].

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2. 

   On the reduction of powers of self-adjoint operators

   Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Salima Kebli --- University of Oran 1, Algeria Mohammed Hichem Mortad --- University of Oran 1, Algeria

   Let T ∈ B(H) be such that Tn is self-adjoint for some with n ≥ 3. The paper’s primary aim is to establish the conditions that lead to the self-adjointness of T. We pay particular attention to the case where...

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3. 

   New properties of some classes of Saphar type operators

   Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Ayoub Ghorbel --- University of Sfax, Tunisia Snežana Č. Živković-Zlatanović --- University of Niš, Serbia

   This paper explores additional properties of some classes of Saphar type operators, namely left Drazin invertible, essentially left Drazin invertible, right Drazin invertible, and essentially right Drazin invertible operators on Banach spaces, building upon the groundwork laid in [8] and...

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