Spectral operators of matrices
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The class of matrix optimization problems (MOPs) has been recognized in recent years to be a powerful tool to model many important applications involving structured low rank matrices within and beyond the optimization community. This trend can be credited to some extent to the exciting developments in emerging fields such as compressed sensing. The Löwner operator, which generates a matrix valued function via applying a single-variable function to each of the singular values of a matrix, has played an important role for a long time in solving matrix optimization problems. However, the classical theory developed for the Löwner operator has become inadequate in these recent applications. The main objective of this paper is to provide necessary theoretical foundations from the perspectives of designing efficient numerical methods for solving MOPs. We achieve this goal by introducing and conducting a thorough study on a new class of matrix valued functions, coined as spectral operators of matrices. Several fundamental properties of spectral operators, including the well-definedness, continuity, directional differentiability and Fréchet-differentiability are systematically studied.
KeywordsSpectral operators Directional differentiability Fréchet differentiability Matrix valued functions Proximal mappings
Mathematics Subject Classification90C25 90C06 65K05 49J50 49J52
We would like to thank the referees as well as the editors for their constructive comments that have helped to improve the quality of the paper. The research of C. Ding was supported by the National Natural Science Foundation of China under projects No. 11301515, No. 11671387 and No. 11531014.
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