In this paper we investigate some matrix structures on C n×n that have a good behaviour under matrix inversion. The first type of structure is closely related to low displacement rank matrices. Next, we show that for a matrix having a low rank submatrix, also the inverse matrix must have a low rank submatrix, which we can explicitly determine. This allows us to generalize a theorem due to Fiedler. The generalization consists in the fact that our rank structures may have their own shift matrix Λ k ∈ C m×m , for suitable m, with Fiedler's theorem corresponding to the limiting cases Λ k → 0 and Λ k → ∞I.Keywords : displacement structures, Hermitian plus low rank, rank structures, lower semiseparable (plus diagonal) matrices, matrix inversion. AMS(MOS) Classification : Primary : 15A09, Secondary : 15A03,65F05.
Structures preserved by matrix inversionSteven Delvaux * , Marc Van Barel *
24th December 2004Abstract In this paper we investigate some matrix structures on C n×n that have a good behaviour under matrix inversion. The first type of structure is closely related to low displacement rank matrices. Next, we show that for a matrix having a low rank submatrix, also the inverse matrix must have a low rank submatrix, which we can explicitly determine. This allows us to generalize a theorem due to Fiedler. The generalization consists in the fact that our rank structures may have their own shift matrix Λ k ∈ C m×m , for suitable m, with Fiedler's theorem corresponding to the limiting cases Λ k → 0 and Λ k → ∞I.