2 problems

Let $n$ be a positive integer. For an $n$-braid diagram, its OU matrix $U(b)$ is the non-negative integer zero-diagonal matrix whose $(i,j)$ entry counts crossings between strands…

Let $n$ be a positive integer, and let $M$ be an $n\times n$ integer matrix. A zero-diagonal matrix is T0 if, whenever $1\leq i<j<k\leq n$, the conditions $M(i,j)=M(j,k)=0$ imply…