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Flexible Time-Frequency Decompositions and Adaptive Treatment of Operator Equations by Frames


The goal of the proposed two year project is to develop a general Banish space theory of time-frequency localized, redundant and stable non-orthogonal expansions (briefly Banish frames) and to study adaptive numerical schemes for (certain) linear (pseudo-differential) operator equations using their matrix representations with respect to such well-localized frames. Whereas the construction of unconditional (rasp. Rises) bases is no problem in the wavelet or Gabon analysis case (due to the group structure in the background) the extra flexibility in the construction of Banish frames is expected to be crucial when one tries to define such Banish frames overbore complex geometries like manifolds. Starting from the known cases of Banish frames of Gabon and wavelet type we want to investigate an intermediate time-frequency localizing family of Banish frames (flexible Wavelet-wavelet frames) generated by a parametric combination of modulations, translations and dilations (parameterised by alpha in [0,1]), applied to some given analysing function (or atom), and use size andsummability conditions on the corresponding coefficients in order to define so called alpha-modulation spaces. This achievement could be interpreted as a generalization of the atomic decomposition and co orbit space theory developed by Hechinger and Grouching around 1990. In fact, for the limiting cases alpha = 0 and alpha = these spaces coincide with modulation rasp. Besot spaces, whose Wavelet- rasp. Wavelet decompositions are characterized by suitable weighted mixed-norm sequence space. A bounded linear operator can be discredited by means of the representation with respect to a time-frequency localizing Banish frame. This gives rise to an equivalent singular (infinite) matrix representation of the operator whose a pseudo-inverse can be efficiently calculated e.g. by means of numerical adaptive schemes based on damped-Richardson iterative algorithm.

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Dr. Karl Lueger-Ring 1

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