Angle criteria for frame sequences and frames containing a Riesz basis |
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| Authors: | Young-Hwa Ha |
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| Affiliation: | a Department of Mathematics, Ajou University, Suwon 442-749, Republic of Korea
b Department of Mathematics, SunKunKwan University, Suwon, Republic of Korea |
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| Abstract: | We obtain a condition implying that the union of two frame sequences is also a frame sequence. Christensen found a condition for this in terms of orthogonal projections. We phrase our condition by use of the angle between closed subspaces. Also a lower bound formula is obtained. We then apply the results to find conditions for a frame containing a Riesz basis to be a Riesz frame. |
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| Keywords: | Angle Frame Riesz frame Riesz basis Excess Near Riesz basis |
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