摘要
Let X be a Hilbert space with the real or complex base field K, the inner product 【·,·】 and the corresponding norm ‖·‖. For any given matrix A = [a<sub>ij</sub>] ∈K<sup>p×q</sup>, we can define a linear mapping （?）: X<sup>q</sup>→X<sup>p</sup>:
基金
Project supported by the National Natural Science Foundation of China
