Screened Poisson equation

In physics, the screened Poisson equation is a Poisson equation, which arises in (for example) the Klein–Gordon equation, electric field screening in plasmas, and nonlocal granular fluidity in granular flow. == Statement of the equation == The equation is [ Δ − λ 2 ] u ( r ) = − f ( r ) , {\displaystyle \left[\Delta -\lambda ^{2}\right]u(\mathbf {r} )=-f(\mathbf {r} ),} where Δ {\displaystyle \Delta } is the Laplace operator, λ is a constant that expresses the "screening", f is an arbitrary function of position (known as the "source function") and u is the function to be determined.

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