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In mathematical analysis, a Hermitian function is a complex function with the property that its complex conjugate is equal to the original function with the variable changed in sign: : (where the overbar indicates the complex conjugate) for all in the domain of . This definition extends also to functions of two or more variables, e.g., in the case that is a function of two variables it is Hermitian if : for all pairs in the domain of . From this definition it follows immediately that: is a Hermitian function if and only if * the real part of is an even function, and * the imaginary part of is an odd function. == Motivation == Hermitian functions appear frequently in mathematics, physics, and signal processing. For example, the following two statements follow from basic properties of the Fourier transform: * The function is real-valued if and only if the Fourier transform of is Hermitian. * The function is Hermitian if and only if the Fourier transform of is real-valued. Since the Fourier transform of a real signal is guaranteed to be Hermitian, it can be compressed using the Hermitian even/odd symmetry. This, for example, allows the discrete Fourier transform of a signal (which is in general complex) to be stored in the same space as the original real signal. * If ''f'' is Hermitian, then . Where the is cross-correlation, and is convolution. * If both ''f'' and ''g'' are Hermitian, then . 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Hermitian function」の詳細全文を読む スポンサード リンク
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