Minimal rank completions for block matrices

Abstract This paper deals with the following problem of completion of block matrices. Let Aij, i ⩾ j, be given matrices. Find additional matrices Aij such that the completion A = (Aij)ni, j = 1 has lowest possible rank. The structure of the set of all minimal rank completions is studied. Special attention is paid to the Toeplitz case together with its connection to the partial realization problem.