Skew-Hermitian or Hermitian Matrix?

In summary, the conversation discusses the differences between Hermitian and Skew-Hermitian matrices. The Homework Equations state that for Hermitian matrices, the matrix A is equal to the transpose of the conjugate of A, while for Skew-Hermitian matrices, A is equal to the negative of the transpose of the conjugate of A. The conversation also mentions that for Skew-Hermitian matrices, the diagonal elements must be zero, while for Hermitian matrices, they can be nonzero but must be purely imaginary. The conversation concludes by noting that Hermitian and Skew-Hermitian matrices complement each other in terms of their diagonals.
  • #1
jaus tail
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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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  • #2
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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  • #3
Yeah. For skew hermitian, the diagonal elements are zero.
 
  • #4
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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  • #5
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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1. What is a Skew-Hermitian or Hermitian Matrix?

A Skew-Hermitian matrix is a type of complex square matrix where the transpose of the matrix is equal to the negative of the complex conjugate of the original matrix. This means that all elements on the main diagonal of the matrix are equal to zero, and the elements above the main diagonal are equal to the negative of the complex conjugates of the elements below the main diagonal. A Hermitian matrix is a special case of a Skew-Hermitian matrix where all elements are real numbers.

2. How are Skew-Hermitian and Hermitian matrices related?

Both Skew-Hermitian and Hermitian matrices are special types of complex square matrices. They are related in that they both have symmetric properties, but they differ in that the elements of a Skew-Hermitian matrix must be complex numbers, while the elements of a Hermitian matrix must be real numbers. Additionally, the transpose of a Hermitian matrix is equal to its complex conjugate, while the transpose of a Skew-Hermitian matrix is equal to the negative of its complex conjugate.

3. What are the applications of Skew-Hermitian and Hermitian matrices?

Skew-Hermitian and Hermitian matrices are used in various fields of science and engineering, such as quantum mechanics, signal processing, and control theory. In quantum mechanics, these matrices are used to represent observables and operators. In signal processing, they are used in image and audio compression. In control theory, they are used to model and analyze systems with complex dynamics.

4. How are Skew-Hermitian and Hermitian matrices computed?

Skew-Hermitian and Hermitian matrices can be computed using various methods, such as the diagonalization method or the Jordan decomposition method. The diagonalization method involves finding the eigenvalues and eigenvectors of the matrix and then using them to construct a diagonal matrix. The Jordan decomposition method involves decomposing the matrix into a sum of a Hermitian matrix and a skew-Hermitian matrix. There are also several algorithms and software packages available for computing these matrices.

5. What are the properties of Skew-Hermitian and Hermitian matrices?

One of the main properties of Skew-Hermitian and Hermitian matrices is that their eigenvalues are always real numbers. Additionally, the diagonal elements of a Hermitian matrix are always real, while the diagonal elements of a Skew-Hermitian matrix are always equal to zero. Another important property is that the product of a Skew-Hermitian matrix and a Hermitian matrix is always a Skew-Hermitian matrix, while the product of two Hermitian matrices is always a Hermitian matrix.

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