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In physics, the Green's function (or fundamental solution) for Laplace's equation in three variables is used to describe the response of a particular type of physical system to a point source. In particular, this Green's function arises in systems that can be described by Poisson's equation, a partial differential equation (PDE) of the form : where is the Laplace operator in , is the source term of the system, and is the solution to the equation. Because is a linear differential operator, the solution to a general system of this type can be written as an integral over a distribution of source given by : : where the Green's function for Laplace's equation in three variables describes the response of the system at the point to a point source located at : : and the point source is given by , the Dirac delta function. ==Motivation== One physical system of this type is a charge distribution in electrostatics. In such a system, the electric field is expressed as the negative gradient of the electric potential, and Gauss's law in differential form applies: : : Combining these expressions gives : (Poisson's equation.) We can find the solution to this equation for an arbitrary charge distribution by temporarily considering the distribution created by a point charge located at : : In this case, : which shows that for will give the response of the system to the point charge . Therefore, from the discussion above, if we can find the Green's function of this operator, we can find to be : for a general charge distribution. 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「Green's function for the three-variable Laplace equation」の詳細全文を読む スポンサード リンク
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