Skew-Hermitian or Hermitian Matrix?

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SUMMARY

The discussion centers on the properties of Hermitian and Skew-Hermitian matrices, specifically their diagonal elements. A Hermitian matrix features entirely real diagonal components, while a Skew-Hermitian matrix has purely imaginary diagonal elements. The confusion arises from the misconception that Skew-Hermitian matrices must have zero diagonal elements; instead, they can have purely imaginary values. The participants clarify that the diagonal elements of Skew-Hermitian matrices do not need to be zero but must satisfy the condition where the conjugate equals the negative of the element itself.

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Homework Statement


upload_2018-1-30_17-7-35-png.png


Homework Equations


For Hermition: A = transpose of conjugate of A
For Skew Hermition A = minus of transpose of conjugate of A

The Attempt at a Solution


I think this answer is C. As Tranpose of conjugate of matrix is this matrix.
Book answer is D.
Am I wrong or is book wrong?
 

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It is obviously Hermitian. It cannot be skew-hermitian. Skew-hermitian matrices cannot have real numbers on the diagonal as the diagonal elements need to satisfy ##z^* = - z##.
 
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Yeah. For skew hermitian, the diagonal elements are zero.
 
jaus tail said:
Yeah. For skew hermitian, the diagonal elements are zero.
This is not correct. The diagonal elements would be purely imaginary but not necessarily zero.
 
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jaus tail said:
Yeah. For skew hermitian, the diagonal elements are zero.

This holds if you are talking about real valued, skew symmetric matrices. But you aren't.
- - - -
the flip side is a Hermitian matrix must have entirely real components on its diagonal.

So Hermitian has purely real diagonal (possibly all zeros). Skew Hermitian has purely imaginary diagonal (possibly all zeros).

This should give you a hint at how these two matrices 'fit together'.
 
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