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  2. Spectrum continuation analysis - Wikipedia

    en.wikipedia.org/wiki/Spectrum_continuation_analysis

    Spectrum continuation analysis (SCA) is a generalization of the concept of Fourier series to non-periodic functions of which only a fragment has been sampled in the time domain. Recall that a Fourier series is only suitable to the analysis of periodic (or finite-domain) functions f(x) with period 2π. It can be expressed as an infinite series ...

  3. Quasicrystal - Wikipedia

    en.wikipedia.org/wiki/Quasicrystal

    There are several ways to mathematically define quasicrystalline patterns. One definition, the "cut and project" construction, is based on the work of Harald Bohr (mathematician brother of Niels Bohr). The concept of an almost periodic function (also called a quasiperiodic function) was studied by Bohr, including work of Bohl and Escanglon. [47]

  4. Spectral density estimation - Wikipedia

    en.wikipedia.org/wiki/Spectral_density_estimation

    General mathematical techniques for analyzing non-periodic functions fall into the category of Fourier analysis. The Fourier transform of a function produces a frequency spectrum which contains all of the information about the original signal, but in a different form.

  5. Periodic function - Wikipedia

    en.wikipedia.org/wiki/Periodic_function

    A periodic function, also called a periodic waveform (or simply periodic wave), is a function that repeats its values at regular intervals or periods. The repeatable part of the function or waveform is called a cycle . [ 1 ]

  6. Trapezoidal rule - Wikipedia

    en.wikipedia.org/wiki/Trapezoidal_rule

    The trapezoidal rule converges rapidly for periodic functions. This is an easy consequence of the Euler-Maclaurin summation formula , which says that if f {\displaystyle f} is p {\displaystyle p} times continuously differentiable with period T {\displaystyle T} ∑ k = 0 N − 1 f ( k h ) h = ∫ 0 T f ( x ) d x + ∑ k = 1 ⌊ p / 2 ⌋ B 2 k ...

  7. Classical XY model - Wikipedia

    en.wikipedia.org/wiki/Classical_XY_model

    The existence of the thermodynamic limit for the free energy and spin correlations were proved by Ginibre, extending to this case the Griffiths inequality. [3]Using the Griffiths inequality in the formulation of Ginibre, Aizenman and Simon [4] proved that the two point spin correlation of the ferromagnetics XY model in dimension D, coupling J > 0 and inverse temperature β is dominated by (i.e ...

  8. NYT ‘Connections’ Hints and Answers Today ... - AOL

    www.aol.com/nyt-connections-hints-answers-today...

    Get ready for all of today's NYT 'Connections’ hints and answers for #584 on Wednesday, January 15, 2025. Today's NYT Connections puzzle for Wednesday, January 15, 2025 The New York Times

  9. Particle in a one-dimensional lattice - Wikipedia

    en.wikipedia.org/wiki/Particle_in_a_one...

    When talking about solid materials, the discussion is mainly around crystals – periodic lattices. Here we will discuss a 1D lattice of positive ions. Assuming the spacing between two ions is a, the potential in the lattice will look something like this: The mathematical representation of the potential is a periodic function with a period a.