Article
Riesz Bases and Multiresolution Analyses
Department of Mathematics, Auburn University, Auburn, Alabama, 368495310, f2zalik@math.auburn.eduf2
Applied and Computational Harmonic Analysis (Impact Factor: 2.04). 11/1999; 7(3):315331. DOI: 10.1006/acha.1999.0274 ABSTRACT
Recently we found a family of nearly orthonormal affine Riesz bases of compact support and arbitrary degrees of smoothness, obtained by perturbing the onedimensional Haar mother wavelet using Bsplines. The mother wavelets thus obtained are symmetric and given in closed form, features which are generally lacking in the orthogonal case. We also showed that for an important subfamily the wavelet coefficients can be calculated in O(n) steps, just as for orthogonal wavelets. It was conjectured by Aldroubi, and independently by the author, that these bases cannot be obtained by a multiresolution analysis. Here we prove this conjecture. The work is divided into four sections. The first section is introductory. The main feature of the second is simple necessary and sufficient conditions for an affine Riesz basis to be generated by a multiresolution analysis, valid for a large class of mother wavelets. In the third section we apply the results of the second section to several examples. In the last section we show that our bases cannot be obtained by a multiresolution analysis.
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 "Over the last years, there has been many achievements in the applications of Riesz bases [12] [25], and a lot of research results about the characterizations and stability of Riesz bases have arisen [6] [11] [24]. Riesz bases, which are equivalent to exact frames in Hilbert spaces, have become a powerful theoretical tool to research signal analysis. "
Article: Exact gframes in Hilbert spaces
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ABSTRACT: Gframes, which were considered recently as generalized frames in Hilbert spaces, have many properties similar to those of frames, but not all the properties are similar. For example, exact frames are equivalent to Riesz bases, but exact gframes are not equivalent to gRiesz bases. In this paper, we firstly give a characterization of an exact gframe in a complex Hilbert space. We also obtain an equivalent relation between an exact gframe and a gRiesz basis under some conditions. Lastly we consider the stability of an exact gframe for a Hilbert space under perturbation. These properties of exact gframes for Hilbert spaces are not similar to those of exact frames. 
 "This requires two steps. The theorem in [5] that provides the basis for Theorem 2.1, only shows in general that the the constructed wavelet is obtained from the GMRA determined by φ, in the sense defined by Zalik [18]. This means only that the wavelet ψ ∈ V 1 . "
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ABSTRACT: A generalized filter construction is used to build nonMRA Parseval wavelets for dilation by 2 in L 2 (R 2). These examples have the same multiplicity functions as wavelet sets, yet can be made to be C r with C r Fourier transform for any fixed positive integer r. 
 "This result is a refinement of Wang's characterization of biorthogonal wavelets associated with an MRA [18]. On the other hand, Zalik [19] has initiated investigation of the class of Riesz wavelets obtained by an MRA by giving a characterization of this class. The natural question concerns the relation between these different notions of Riesz wavelets. "
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ABSTRACT: We investigate Riesz wavelets in the context of generalized multiresolution analysis (GMRA). In particular, we show that Zalik's class of Riesz wavelets obtained by an MRA is the same as the class of biorthogonal wavelets associated with an MRA.