单词	Dirac delta function
释义	Dirac delta function The Dirac delta function δ(x) has defining properties , and δ(x) = 0 for x ≠ 0. No function, in the traditional sense, has these properties, but δ(x) can be rigorously understood as the Schwartz distribution δ(φ) = φ(0), where φ is a test function. The delta function is useful for modelling point masses or charges, or instantaneous impulses. As a distribution it is the derivative of the Heaviside function. See sifting property.
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