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Rank of adjoint operator

  1. Feb 5, 2010 #1
    I have a question about the rank of adjoint operator....

    Let T : V → W be a linear transformation where V and W are finite-dimensional inner product spaces with inner products <‧,‧> and <‧,‧>' respectively. A funtion T* : W → V is called an adjoint of T if <T(x),y>' = <x,T*(x)> for all x in V and y in W.

    My question is how to prove that rank(T*) = rank(T)??

    Can anyone give me some tips, thanks^^
  2. jcsd
  3. Feb 5, 2010 #2


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    Take a basis B of V and a basis B' of W in which the matrix of <,> and <,>' are both the identity. That is to say, pick B <,>-orthonormal and B' <,>'-orthonormal. This is always possible by Gram-Schmidt.

    Then write the equation <T(x),y>' = <x,T*(x)> in matrix form with respect of these basis and conclude.
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