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#### Keywords

Semipositive matrix, minimally semipositive matrix, principal pivot transform, Moore-Penrose inverse, left inverse, interval of matrices

#### Abstract

Semipositive matrices (matrices that map at least one nonnegative vector to a positive vector) and minimally semipositive matrices (semipositive matrices whose no column-deleted submatrix is semipositive) are well studied in matrix theory. In this article, this notion is revisited and new results are presented. It is shown that the set of all $m \times n$ minimally semipositive matrices contains a basis for the linear space of all $m \times n$ matrices. Apart from considerations involving principal pivot transforms and the Schur complement, results on semipositivity and/or minimal semipositivity for the following classes of matrices are presented: intervals of rectangular matrices, skew-symmetric and almost skew-symmetric matrices, copositive matrices, $N$-matrices, almost $N$-matrices and almost $P$-matrices.

abs_vol34_pp35-53.pdf (106 kB)
Abstract

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