Some Characterizations of Nekrasov and S-Nekrasov Matrices.

It is known that the Nekrasov and S-Nekrasov matrices form subclasses of (nonsingular) H-matrices. The paper presents some necessary and sufficient conditions for a square matrix with complex entries to be a Nekrasov and an S-Nekrasov matrix. In particular, characterizations of the Nekrasov and S-Nekrasov matrices in terms of the diagonal column scaling matrices transforming them into strictly diagonally dominant matrices are obtained. Bibliography: 15 titles. [ABSTRACT FROM AUTHOR]