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Affine frames, GMRA's, and the canonical dual

Marcin Bownik, Eric Weber (2003)

Studia Mathematica

We show that if the canonical dual of an affine frame has the affine structure, with the same number of generators, then the core subspace V₀ is shift invariant. We demonstrate, however, that the converse is not true. We apply our results in the setting of oversampling affine frames, as well as in computing the period of a Riesz wavelet, answering in the affirmative a conjecture of Daubechies and Han. Additionally, we completely characterize when the canonical dual of a quasi-affine frame has the...

Almost everywhere summability of Laguerre series

Krzysztof Stempak (1991)

Studia Mathematica

We apply a construction of generalized twisted convolution to investigate almost everywhere summability of expansions with respect to the orthonormal system of functions ℓ n a ( x ) = ( n ! / Γ ( n + a + 1 ) ) 1 / 2 e - x / 2 L n a ( x ) , n = 0,1,2,..., in L 2 ( ℝ + , x a d x ) , a ≥ 0. We prove that the Cesàro means of order δ > a + 2/3 of any function f ∈ L p ( x a d x ) , 1 ≤ p ≤ ∞, converge to f a.e. The main tool we use is a Hardy-Littlewood type maximal operator associated with a generalized Euclidean convolution.

Almost everywhere summability of Laguerre series. II

K. Stempak (1992)

Studia Mathematica

Using methods from [9] we prove the almost everywhere convergence of the Cesàro means of Laguerre series associated with the system of Laguerre functions L n a ( x ) = ( n ! / Γ ( n + a + 1 ) ) 1 / 2 e - x / 2 x a / 2 L n a ( x ) , n = 0,1,2,..., a ≥ 0. The novel ingredient we add to our previous technique is the A p weights theory. We also take the opportunity to comment and slightly improve on our results from [9].

An algebraic construction of discrete wavelet transforms

Jaroslav Kautský (1993)

Applications of Mathematics

Discrete wavelets are viewed as linear algebraic transforms given by banded orthogonal matrices which can be built up from small matrix blocks satisfying certain conditions. A generalization of the finite support Daubechies wavelets is discussed and some special cases promising more rapid signal reduction are derived.

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