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Hermitian and Anti Hermitian Matrices

  1. Hermitian Matrix: Any Complex Square Matrix is called a Hermitian Matrix if the Elements present in it's \(i^{th}\) Row and \(j^{th}\) Column are Complex Conjugates of Elements present in it's \(j^{th}\) Row and \(i^{th}\) Column and has Only Real Values in the Main Diagonal. That is, for any Hermitian Matrix \(A\), \(a_{ij}=\overline{a_{ji}}\) for all \(i\neq j\). Following are some examples of Hermitian Matrices

    \(\begin{bmatrix} -2 & 3+2i & 5-4i\\ 3-2i & 1 & 6-2i\\ 5+4i & 6+2i & -5\end{bmatrix}\hspace{.5cm} \begin{bmatrix} 3.5 & -3+7i \\ -3-7i & 0 \end{bmatrix}\)

    Please note that for any Hermitian Matrix \(A\), the Conjugate Transpose of the Matrix is the Matrix itself. That is

    \(A^\dagger=A\)
  2. Anti-Hermitian Matrix: Any Square Matrix is called a Anti-Hermitian Matrix if all its Main Diagona are either 0 or Pure Imaginary Values and the Elements present in it's \(i^{th}\) Row and \(j^{th}\) Column are Negative of Complex Conjugates of the Elements present in it's \(j^{th}\) Row and \(i^{th}\) Column. That is, for any Anti-Hermitian Matrix \(A\), \(a_{ij}=-\overline{a_{ji}}\) for all \(i\neq j\). Following are some examples of Anti-Hermitian Matrices

    \(\begin{bmatrix} 7i & -1.5+4i & 4+4i\\ 1.5+4i & 0 & -.3+7i\\ -4+4i & .3+7i & 0\end{bmatrix}\hspace{.5cm} \begin{bmatrix} 4i & 1.23+5i \\ -1.23+5i & 2i \end{bmatrix}\)

    Please note that for any Anti-Hermitian Matrix \(A\), the Conjugate Transpose of the Matrix is the negative of the Matrix. That is

    \(A^\dagger=-A\)
  3. Any Complex Square Matrix \(A\) can be converted to a pair of Hermitian and Anti-Hermitian Matrices by using the following formula

    Hermitian Matrix = \({\Large\frac{A + A^\dagger}{2}}\)
    Anti-Hermitian Matrix = \({\Large\frac{A - A^\dagger}{2}}\)
  4. Conversely, given any pair of Hermitian and Anti-Hermitian Matrices, the Original Complex Matrix can be obtained by adding the 2 Matrices.
Related Calculators
Symmetric/Skew-Symmetric and Hermitian/Anti-Hermitian Matrix Calculator
Related Topics
Symmetric and Skew Symmetric Matrices,    Introduction to Matrix Algebra
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