Farid, AilaneFaris, BoudjellalSouheyb, Dehimi: SupervisorAbdelhamid, Tallab: Co-Supervisor2024-07-112024-07-112024https://dspace.univ-msila.dz/handle/123456789/43616In this work, we study the powers of closed linear operators. We showed that If a closed operator T is quasinormal and its power Tn is normal with n≥2, then T must be normal. We also presented a generalization of a result related to J.von Neumann’s result. The nth roots of quasinormal operators also have been studied.enBézout’s theorem in arithmeticclosed operatorshyponormal operatorsnormal operatorspowers of operatorsquasinormal operatorsself-adjoint operatorsThesis