Definition 1.1. [8] An oriented knotK is a topologically slice knot if there is an oriented embedded locally flat disk D2 ⊆ D4 whose boundary ∂D2 ⊂ ∂D4 = S3 is the knot K. Here locally flat means locally homeomorphic to a standardly embedded R2 ⊆ R4. Two knots K1,K2 are concordant if there is an embedded locally flat annulus S 1 × I ⊂ S3 × I such that ∂(S1×I) ⊆ S3×I is the disjoint union of the...