Malgrange–Ehrenpreis theorem

A key question in mathematics and physics is how to model empty space with a point source, like the effect of a point mass on the gravitational potential energy, or a point heat source on a plate. Such physical phenomena are modeled by partial differential equations, having the form L ϕ = δ {\displaystyle L\phi =\delta } , where L {\displaystyle L} is a linear differential operator and δ {\displaystyle \delta } is a delta function representing the point source.

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