Conjugate transpose: Difference between revisions

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[[Category:Matrices]]
[[Category:Matrices]]


Suppose that a &nbsp; [[matrix]] &nbsp; <big><math>M</math></big> &nbsp; contains &nbsp; [[Arithmetic/Complex|complex numbers]]. &nbsp; Then the &nbsp; [[wp:conjugate transpose|conjugate transpose]] &nbsp; of &nbsp; <math>M</math> &nbsp; is a matrix &nbsp; <math>M^H</math> &nbsp; containing the &nbsp; [[complex conjugate]]s &nbsp; of the [[matrix transposition]] &nbsp; of &nbsp; <math>M.</math>
Suppose that a [[matrix]] <big><math>M</math></big> contains [[Arithmetic/Complex|complex numbers]]. Then the [[wp:conjugate transpose|conjugate transpose]] of <math>M</math> is a matrix <math>M^H</math> containing the [[complex conjugate]]s of the [[matrix transposition]] of <math>M</math>.


::: <big><big><math>(M^H)_{ji} = \overline{M_{ij}}</math></big></big>
::: <big><math>(M^H)_{ji} = \overline{M_{ij}}</math></big>




This means that &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; row &nbsp; <big><math>j,</math></big> &nbsp; column &nbsp; <big><math>i</math></big> &nbsp; of the conjugate transpose equals the
This means that row <big><math>j</math></big>, column <big><math>i</math></big> of the conjugate transpose equals the
<br>complex conjugate of &nbsp; row &nbsp; <big><math>i,</math></big> &nbsp; column &nbsp; <big><math>j</math></big> &nbsp; of the original matrix.
<br>complex conjugate of row <big><math>i</math></big>, column <big><math>j</math></big> of the original matrix.




In the next list, &nbsp; <big><math>M</math></big> &nbsp; must also be a square matrix.
In the next list, <big><math>M</math></big> must also be a square matrix.


* A [[wp:Hermitian matrix|Hermitian matrix]] equals its own conjugate transpose: &nbsp; <big><math>M^H = M.</math></big>
* A [[wp:Hermitian matrix|Hermitian matrix]] equals its own conjugate transpose: <math>M^H = M</math>.
* A [[wp:normal matrix|normal matrix]] is commutative in [[matrix multiplication|multiplication]] with its conjugate transpose: &nbsp; <big><math>M^HM = MM^H.</math></big>
* A [[wp:normal matrix|normal matrix]] is commutative in [[matrix multiplication|multiplication]] with its conjugate transpose: <math>M^HM = MM^H</math>.
* A [[wp:unitary matrix|unitary matrix]] has its [[inverse matrix|inverse]] equal to its conjugate transpose: &nbsp; <big><math>M^H = M^{-1}.</math></big> <br> This is true when: <br> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [[wikt:iff|'''iff''']] &nbsp; <math>M^HM = I_n</math> &nbsp; and <br> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [[wikt:iff|'''iff''']] &nbsp; <big><math>MM^H = I_n,</math></big> &nbsp; where &nbsp; <big><math>I_n</math></big> &nbsp; is the identity matrix.
* A [[wp:unitary matrix|unitary matrix]] has its [[inverse matrix|inverse]] equal to its conjugate transpose: <math>M^H = M^{-1}</math>. <br> This is true [[wikt:iff|iff]] <math>M^HM = I_n</math> and iff <math>MM^H = I_n</math>, where <math>I_n</math> is the identity matrix.




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Also determine if the matrix is a:
Also determine if the matrix is a:
::* &nbsp; Hermitian matrix,
::* Hermitian matrix,
::* &nbsp; normal matrix, &nbsp; &nbsp; or
::* normal matrix, or
::* &nbsp; unitary matrix.
::* unitary matrix.




;See also:
;See also:
* &nbsp; MathWorld entry: &nbsp; [http://mathworld.wolfram.com/ConjugateTranspose.html conjugate transpose]
* MathWorld entry: [http://mathworld.wolfram.com/ConjugateTranspose.html conjugate transpose]
* &nbsp; MathWorld entry: &nbsp; [http://mathworld.wolfram.com/HermitianMatrix.html Hermitian matrix]
* MathWorld entry: [http://mathworld.wolfram.com/HermitianMatrix.html Hermitian matrix]
* &nbsp; MathWorld entry: &nbsp; [http://mathworld.wolfram.com/NormalMatrix.html normal matrix]
* MathWorld entry: [http://mathworld.wolfram.com/NormalMatrix.html normal matrix]
* &nbsp; MathWorld entry: &nbsp; [http://mathworld.wolfram.com/UnitaryMatrix.html unitary matrix]
* MathWorld entry: [http://mathworld.wolfram.com/UnitaryMatrix.html unitary matrix]
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