Displaying similar documents to “On the Jacobian ideal of the binary discriminant.”

Positive polynomials and hyperdeterminants

Fernando Cukierman (2007)

Collectanea Mathematica

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Let be a homogeneous real polynomial of even degree in any number of variables. We consider the problem of giving explicit conditions on the coefficients so that is positive definite or positive semi-definite. In this note we produce a necessary condition for positivity, and a sufficient condition for non-negativity, in terms of positivity or semi-positivity of a one-variable of . Also, we revisit the known sufficient condition in terms of Hankel matrices.

Ultrasymmetric sequence spaces in approximation theory.

Evgeniy Pustylnik (2006)

Collectanea Mathematica

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Let φ(t) be a positive increasing function and let Ê be an arbitrary sequence space, rearrangement-invariant with respect to the atomic measure µ(n) = 1/n. Let {a*} mean the decreasing rearrangement of a sequence {|a|}. A sequence space l with symmetric (quasi)norm || {φ(n)a*} || is called , because it is not only intermediate but also interpolation between the corresponding Lorentz and Marcinkiewicz spaces Λ and M. We study properties of the spaces l for all admissible parameters φ,...

Wiener amalgam spaces for the fundamental identity of Gabor analysis.

Hans G. Feichtinger, Franz Luef (2006)

Collectanea Mathematica

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In the last decade it has become clear that one of the central themes within Gabor analysis (with respect to general time-frequency lattices) is a duality theory for Gabor frames, including the Wexler-Raz biorthogonality condition, the Ron-Shen duality principle and the Janssen representation of a Gabor frame operator. All these results are closely connected with the so-called , which we derive from an application of Poisson's summation formula for the symplectic Fourier transform. The...