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In this paper, we analyze the uniqueness of the sparse time frequency decomposition and investigate the eciency of the nonlinear matching pursuit method. Under the assumption of scale separation, we show that the sparse time frequency decomposition is unique up to an error that is determined by the scale separation property of the signal. We further show that the unique decomposition can be obtained approximately by the sparse time frequency decomposition using nonlinear matching pursuit.

A not necessarily continuous, linear or multiplicative function from an algebra A into itself is called a local automorphism if agrees with an automorphism of A at each point in A. In this paper, we study the question when a local automorphism of a C*-algebra, or a W*-algebra, is an automorphism.