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  2. Dirac delta function - Wikipedia

    en.wikipedia.org/wiki/Dirac_delta_function

    A Dirac comb is an infinite series of Dirac delta functions spaced at intervals of T. A so-called uniform "pulse train" of Dirac delta measures, which is known as a Dirac comb, or as the Sha distribution, creates a sampling function, often used in digital signal processing (DSP) and discrete time signal analysis

  3. Duhamel's integral - Wikipedia

    en.wikipedia.org/wiki/Duhamel's_integral

    If a system initially rests at its equilibrium position, from where it is acted upon by a unit-impulse at the instance t=0, i.e., p(t) in the equation above is a Dirac delta function δ(t), () = | = =, then by solving the differential equation one can get a fundamental solution (known as a unit-impulse response function)

  4. Feynman parametrization - Wikipedia

    en.wikipedia.org/wiki/Feynman_parametrization

    1 Formulas. 2 Derivation. 3 Alternative form. ... More generally, using the Dirac delta function ... Feynman Integral Calculus, ...

  5. Bell-shaped function - Wikipedia

    en.wikipedia.org/wiki/Bell-shaped_function

    Some bell shaped functions, such as the Gaussian function and the probability distribution of the Cauchy distribution, can be used to construct sequences of functions with decreasing variance that approach the Dirac delta distribution. [1] Indeed, the Dirac delta can roughly be thought of as a bell curve with variance tending to zero.

  6. Functional derivative - Wikipedia

    en.wikipedia.org/wiki/Functional_derivative

    A formula to determine functional derivatives for a common class of functionals can be written as the integral of a function and its derivatives. This is a generalization of the Euler–Lagrange equation : indeed, the functional derivative was introduced in physics within the derivation of the Lagrange equation of the second kind from the ...

  7. Green's function - Wikipedia

    en.wikipedia.org/wiki/Green's_function

    Then the integral (′) (′) ′ reduces to simply φ(x) due to the defining property of the Dirac delta function and we have = (, ′) (′) ′ + [(′) ′ (, ′) (, ′) ′ (′)] ^ ′. This form expresses the well-known property of harmonic functions , that if the value or normal derivative is known on a bounding surface, then the ...

  8. Dirac comb - Wikipedia

    en.wikipedia.org/wiki/Dirac_comb

    The graph of the Dirac comb function is an infinite series of Dirac delta functions spaced at intervals of T. In mathematics, a Dirac comb (also known as sha function, impulse train or sampling function) is a periodic function with the formula ⁡ := = for some given period . [1]

  9. Dirac measure - Wikipedia

    en.wikipedia.org/wiki/Dirac_measure

    The Dirac measures are the extreme points of the convex set of probability measures on X. The name is a back-formation from the Dirac delta function; considered as a Schwartz distribution, for example on the real line, measures can be taken to be a special kind of distribution. The identity