Speaker: Prof. SHEN Yi, Professor, Department of Mathematical Sciences, Zhejiang Sci-Tech University
Tencent Meeting ID: 951 684 427 （passcode: 310027）
We consider sparse representations of signals from redundant dictionaries which are unions of several orthonormal bases. The spark introduced by Donoho and Elad plays an important role in sparse representations. However, numerical computations of sparks are generally combinatorial. For unions of several orthonormal bases, two lower bounds on the spark via the mutual coherence were established in previous work. We constructively prove that both of them are tight. Our main results give positive answers to Gribonval and Nielsen's open problem on sparse representations in unions of orthonormal bases. Constructive proofs rely on a family of mutual unbiased bases which first appears in quantum information theory.It is joint work with Prof. Song Li, Dr. Yuan Shen and Chenyun Yu.