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The Sommerfeld identity is a mathematical identity, due Arnold Sommerfeld, used in the theory of propagation of waves, : where : is to be taken with positive real part, to ensure the convergence of the integral and its vanishing in the limit and :. Here, is the distance from the origin while is the distance from the central axis of a cylinder as in the cylindrical coordinate system. The function is a Bessel function. Here the notation for Bessel functions follows the German convention, to be consistent with the original notation used by Sommerfeld. In English literature it is more common to use :. This identity is known as the Sommerfeld Identity (). An alternative form is : Where : (). The notation used here is different form that above: is now the distance from the origin and is the axial distance in a cylindrical system defined as . The physical interpretation is that a spherical wave can be expanded into a summation of cylindrical waves in direction, multiplied by a plane wave in the direction; see the Jacobi-Anger expansion. The summation has to be taken over all the wavenumbers . == References == # Sommerfeld, A.,''Partial Differential Equations in Physics'',Academic Press,New York,1964 # Chew, W.C.,''Waves and Fields in Inhomogeneous Media'',Van Nostrand Reinhold,New York,1990 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「Sommerfeld identity」の詳細全文を読む スポンサード リンク
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