On 2- Self_adjoint Operators

Abstract

In this paper we give a generalization of self-adjoint operators defined on a Hilbert space which we called 2-self-adjoint operators. In spite of that we established some characterizations and properties of such type of operators .Moreover we have found some of their relationships with the other classes of operators .Futhermore ,we study the spectrum of this type of operators

Keywords: Operators on Hilbert space ,Self-adjoint operator,Hyponormal operator,2-normal operators,n-power normal operator,Quasi-posinormal operator.