2 problems

Cochran–Orr conjecture. A link in $S^3$ is null $k$-cobordant if and only if all its Milnor $\overline{\mu}$-invariants of lengths $j$, $1\le j\le 2k$, are zero.

Let oriented links be related by self $\Delta$-equivalence when one can be transformed into the other by self delta moves and ambient isotopies, where each self delta move has all…