Topological ribbon concordance partial-order conjecture

Let $\geq_{\operatorname{top}}$ denote the topological ribbon concordance relation on knots. Topological ribbon concordance conjecture. The relation $\geq_{\operatorname{top}}$ is a partial order on the set of knots. This is the topological analogue of Gordon's conjecture for smooth ribbon concordance. The paper explains that injectivity of the map on fundamental groups is included in the definition because, without it, Freedman's work gives concordances from the unknot to every Alexander polynomial one knot, obstructing the analogous partial-order claim.