Sign patterns that allow minimal semipositivity
An \(n \times m\) matrix with real entries \(A\) is semipositive if \(Ax > 0\) (where the inequality is entrywise) for some \(x \geq 0\). \(A\) is minimally semipositive if it is semipositive and no column-deleted submatrix of it is semipositive. The sign patterns of minimally semipositive matrices which have no zero entries are characterized. Of independent interest is a result on complete bipartite subgraphs of bipartite graphs.
scientific article; zbMATH DE number 778265