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Nov
15
comment Moore-Penrose question
Felix, a reverse order law for the triple product might give some nice answer. For instance, see R. Hartwig, The reverse order law revisited, Linear Algebra Appl., 76 (1986), 241-246.
Nov
6
answered Approximating commuting matrices by commuting diagonalizable matrices
Oct
15
awarded  Teacher
Oct
14
answered Duality between extremal points and extremal maps
Oct
6
comment Sufficient conditions for inverse-positivity
What about semipositivity ? An $m \times n$ matrix is said to be semipositive if there exists $x \in \mathbb{R}^n_+$ such that $Ax \in int(\mathbb{R}^m_+)$; $A$ is said to be minimally semipositive if in addition to being semipositive, no proper $m \times p$ submatrix is semipositive. For a square matrix, minimal semipositivity is the same as inverse positivity. I do not know if MSP is easy to verify. Two references are : Johnson, Kerr and Stanford, Semipositivity of matrices, LAMA, 37(4) (1994), 265-271 and H.J Werner, Characterizations of semipositivity, LAMA, 37(4) (1994), 273-278.
Oct
5
awarded  Editor
Oct
5
revised Sufficient conditions for inverse-positivity
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Oct
5
answered Sufficient conditions for inverse-positivity