Whitney towers, gropes and Casson–Gordon style invariants of links

In this paper, we prove a conjecture of Friedl and Powell that their Casson–Gordon type invariant of 2–component links with linking number one is actually an obstruction to being height-3:5 Whitney tower/grope concordant to the Hopf link. The proof employs the notion of solvable cobordism of 3–manifolds with boundary, which was introduced by Cha. We also prove that the Blanchfield form and the Alexander polynomial of links in S³ give obstructions to height-3 Whitney tower/grope concordance. This generalizes the results of Hillman and Kawauchi.