Let H1 and H2 be Hilbert spaces..If T:H1-->H2 is a bounded linear transformation with M1 closed subspace of H1 and M2 closed subspace of H2 then show that T(M1) is contained in M2 if and only if T*(M2) is contained in M1..

Any help appreciated.

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- Jan 14th 2011, 10:02 PMrishirichHilbert spaces
Let H1 and H2 be Hilbert spaces..If T:H1-->H2 is a bounded linear transformation with M1 closed subspace of H1 and M2 closed subspace of H2 then show that T(M1) is contained in M2 if and only if T*(M2) is contained in M1..

Any help appreciated. - Jan 15th 2011, 12:29 AMOpalg
- Jan 15th 2011, 10:04 PMrishirich
Hey thank you for your reply..Why is the question wrong?

- Jan 16th 2011, 12:53 AMOpalg
The simplest way to see that it is wrong is to think about what happens if and . Then the question is saying that if a subspace is invariant under then it is also invariant under . That is certainly not true. For example, in a 2-dimensional space, the subspace spanned by the second basis vector is invariant under the transformation with matrix , but not under its adjoint.