Proof regarding the image and kernel of a normal operator

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SUMMARY

The discussion centers on proving that if an operator T is normal, then T and its adjoint T* share the same kernel and image. The proof involves demonstrating that Ker T is equal to Ker T* and similarly for their images. The participants highlight the importance of T being unitarily diagonalizable, represented as T = U D U*, where D is a diagonal matrix of eigenvalues. This diagonalization is crucial for understanding the relationship between the kernels and images of T and T*.

PREREQUISITES
  • Understanding of normal operators in functional analysis
  • Knowledge of unitary diagonalization and its implications
  • Familiarity with kernel and image concepts in linear algebra
  • Basic grasp of eigenvalues and eigenvectors
NEXT STEPS
  • Study the properties of normal operators in Hilbert spaces
  • Learn about the spectral theorem for normal operators
  • Explore the implications of unitary transformations on eigenvalues
  • Investigate the relationship between left and right nullspaces in linear operators
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Mathematicians, graduate students in functional analysis, and anyone studying linear operators and their properties in advanced mathematics.

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Homework Statement


Show that if T is normal, then T and T* have the same kernel and the same image.

Homework Equations


N/A

The Attempt at a Solution


At first I tried proving that Ker T ⊆ Ker T* and Ker T* ⊆ Ker, thus proving Ker T = Ker T* and doing the same thing with I am T, but could not find a way of doing so. I am relatively certain this has to do with discomposing T into direct sum subspace or doing something with the orthonormal basis of V comprised of eigenvalues of T but I cannot seem to figure it out.
I would love some assistance on the matter.
 
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You understand that ##T## is unitarily diagonalizable here, right? You really can't ask for much more as the mutually orthonormal eigenvectors form a partition (and indeed are a proper, length preserving, coordinate system).

##T = U D U^*##

##T^* = \big(U D U^*\big)^* = U D^* U^*##

with respect to the the right nullspace, how would you identify it in ##T##, above? What would it look like in ##T^*##? If you are so interested, what would the left nullspace look like for both of them?
 

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