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  2. Sylvester's criterion - Wikipedia

    en.wikipedia.org/wiki/Sylvester's_criterion

    In mathematics, Sylvester’s criterion is a necessary and sufficient criterion to determine whether a Hermitian matrix is positive-definite. Sylvester's criterion states that a n × n Hermitian matrix M is positive-definite if and only if all the following matrices have a positive determinant: the upper left 1-by-1 corner of M,

  3. Definite matrix - Wikipedia

    en.wikipedia.org/wiki/Definite_matrix

    In mathematics, a symmetric matrix with real entries is positive-definite if the real number is positive for every nonzero real column vector, where is the row vector transpose of . [1] More generally, a Hermitian matrix (that is, a complex matrix equal to its conjugate transpose) is positive-definite if the real number is positive for every nonzero complex column vector , where denotes the ...

  4. Williamson theorem - Wikipedia

    en.wikipedia.org/wiki/Williamson_theorem

    The derivation of the result hinges on a few basic observations: The real matrix / /, with (), is well-defined and skew-symmetric.; Any skew-symmetric real matrix can be block-diagonalized via orthogonal real matrices, meaning there is () such that = with a real positive-definite diagonal matrix containing the singular values of .

  5. Schur product theorem - Wikipedia

    en.wikipedia.org/wiki/Schur_product_theorem

    In mathematics, particularly in linear algebra, the Schur product theorem states that the Hadamard product of two positive definite matrices is also a positive definite matrix. The result is named after Issai Schur [ 1 ] (Schur 1911, p. 14, Theorem VII) (note that Schur signed as J. Schur in Journal für die reine und angewandte Mathematik .

  6. Cholesky decomposition - Wikipedia

    en.wikipedia.org/wiki/Cholesky_decomposition

    In linear algebra, the Cholesky decomposition or Cholesky factorization (pronounced / ʃ ə ˈ l ɛ s k i / shə-LES-kee) is a decomposition of a Hermitian, positive-definite matrix into the product of a lower triangular matrix and its conjugate transpose, which is useful for efficient numerical solutions, e.g., Monte Carlo simulations.

  7. Why isn't vaccination proof required for domestic flights? - AOL

    www.aol.com/news/why-isnt-vaccination-proof...

    Calls are rising for airlines to require vaccination proof for domestic passengers. Airlines aren't happy about the idea.

  8. Vaccine mandates: Here are the companies requiring proof of ...

    www.aol.com/finance/companies-requiring-proof...

    Southeastern grocer Publix is giving its employees $125 gift cards when providing proof of vaccination. Starbucks employees will receive up to four hours of paid time for vaccine dosage appointments.

  9. Controllability Gramian - Wikipedia

    en.wikipedia.org/wiki/Controllability_Gramian

    This makes a positive definite matrix. More properties of controllable systems can be found in Chen (1999 , p. 145 ), as well as the proof for the other equivalent statements of “The pair ( A , B ) {\displaystyle ({\boldsymbol {A}},{\boldsymbol {B}})} is controllable” presented in section Controllability in LTI Systems.