Inverse eigenvalue problems of tridiagonal symmetric matrices and tridiagonal bisymmetric matrices

摘要

The problem of generating a matrix A with specified eigenpairs, where A is a tridiagonal symmetric matrix, is presented. A general expression of such a matrix is provided, and the set of such matrices is denoted by S_E. Moreover, the corresponding least-squares problem under spectral constraint is considered when the set S_E is empty, and the corresponding solution set is denoted by S_L. The best approximation problem associated with S_E(S_L) is discussed, that is: to find the nearest matrix A in S_E(S_L) to a given matrix. The existence and uniqueness of the best approximation are proved and the expression of this nearest matrix is provided. At the same time, we also discuss similar problems when A is a tridiagonal bisymmetric matrix.