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  2. Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Fourier_transform

    That there is no one preferred way (often, one says "no canonical way") to compare the two versions of the real line which are involved in the Fourier transform—fixing the units on one line does not force the scale of the units on the other line—is the reason for the plethora of rival conventions on the definition of the Fourier transform.

  3. Dirac delta function - Wikipedia

    en.wikipedia.org/wiki/Dirac_delta_function

    This is, of course, shorthand for the assertion that the Fourier transform of the tempered distribution = is ^ = which again follows by imposing self-adjointness of the Fourier transform. By analytic continuation of the Fourier transform, the Laplace transform of the delta function is found to be [ 66 ] ∫ 0 ∞ δ ( t − a ) e − s t d t ...

  4. Discrete Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Discrete_Fourier_transform

    Fourier transform (bottom) is zero except at discrete points. The inverse transform is a sum of sinusoids called Fourier series. Center-right: Original function is discretized (multiplied by a Dirac comb) (top). Its Fourier transform (bottom) is a periodic summation of the original transform.

  5. Canonical commutation relation - Wikipedia

    en.wikipedia.org/wiki/Canonical_commutation_relation

    According to the correspondence principle, in certain limits the quantum equations of states must approach Hamilton's equations of motion.The latter state the following relation between the generalized coordinate q (e.g. position) and the generalized momentum p: {˙ = = {,}; ˙ = = {,}.

  6. Position and momentum spaces - Wikipedia

    en.wikipedia.org/wiki/Position_and_momentum_spaces

    Conversely, the inverse Fourier transform of a momentum space function is a position space function. These quantities and ideas transcend all of classical and quantum physics, and a physical system can be described using either the positions of the constituent particles, or their momenta, both formulations equivalently provide the same ...

  7. Fourier analysis - Wikipedia

    en.wikipedia.org/wiki/Fourier_analysis

    The inverse transform, known as Fourier series, is a representation of () in terms of a summation of a potentially infinite number of harmonically related sinusoids or complex exponential functions, each with an amplitude and phase specified by one of the coefficients:

  8. Propagator - Wikipedia

    en.wikipedia.org/wiki/Propagator

    In quantum mechanics and quantum field theory, the propagator is a function that specifies the probability amplitude for a particle to travel from one place to another in a given period of time, or to travel with a certain energy and momentum.

  9. Multidimensional transform - Wikipedia

    en.wikipedia.org/wiki/Multidimensional_transform

    The 2D Z-transform, similar to the Z-transform, is used in multidimensional signal processing to relate a two-dimensional discrete-time signal to the complex frequency domain in which the 2D surface in 4D space that the Fourier transform lies on is known as the unit surface or unit bicircle.