2 problems

Let ${\cal A}$ be a sign pattern, and let $mr({\cal A})$ denote its minimum rank over the reals while $mr_{\mathbb Q}({\cal A})$ denotes its minimum rank over the rationals. Ration…

Let $B$, $C$, and $E$ be real matrices satisfying … The zero entries of $E$ are contained in a submatrix with either 2 rows or 2 columns. Rational realization conjecture. There exi…