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self-adjoint operator (Definition)

A densely defined linear operator $ A\colon\mathscr{D}(A)\subset \mathscr{H}\to\mathscr{H}$ on a Hilbert space $ \mathscr{H}$ is a Hermitian or symmetric operator if $ (Ax,y) = (x,Ay)$ for all $ x,y\in \mathscr{D}(A)$. This means that the adjoint $ A^*$ of $ A$ is defined at least on $ \mathscr{D}(A)$ and that its restriction to that set coincides with $ A$. This fact is often denoted by $ A\subset A^*$.

The operator $ A$ is self-adjoint if it coincides with its adjoint, i.e. if $ A=A^*$. If $ A$ is closable and its closure coincides with its adjoint (i.e. $ \overline{A}=A^*$), then $ A$ is said to be essentially self-adjoint.



"self-adjoint operator" is owned by Koro.
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See Also: Hermitian matrix

Also defines:  Hermitian operator, symmetric operator, essentially self-adjoint, self-adjoint
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Cross-references: closure, closable, restriction, adjoint, operator, Hilbert space, linear operator, densely defined
There are 17 references to this entry.

This is version 5 of self-adjoint operator, born on 2003-07-28, modified 2006-06-15.
Object id is 4527, canonical name is SelfAdjointOperator.
Accessed 14042 times total.

Classification:
AMS MSC47B15 (Operator theory :: Special classes of linear operators :: Hermitian and normal operators )
 47B25 (Operator theory :: Special classes of linear operators :: Symmetric and selfadjoint operators )

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