Knot Floer homology and relative adjunction inequalities

TL;DR

This paper introduces new inequalities called relative adjunction inequalities that relate the genera of smooth cobordisms between knots, refining existing inequalities by incorporating knot invariants from Heegaard Floer homology, with applications to concordance and link detection.

Contribution

It establishes relative adjunction inequalities that improve upon classical inequalities by integrating Floer homology invariants, leading to new concordance invariants and applications to link theory.

Findings

Derived new relative adjunction inequalities for knots and links.

Produced concordance invariants for knots in general 3-manifolds.

Reproved the link Milnor conjecture and detected strongly quasipositive fibered links.

Abstract

We establish inequalities that constrain the genera of smooth cobordisms between knots in 4-dimensional cobordisms. These "relative adjunction inequalities" improve the adjunction inequalities for closed surfaces which have been instrumental in many topological applications of gauge theory. The relative inequalities refine the latter by incorporating numerical invariants of knots in the boundary associated to Heegaard Floer homology classes determined by the 4-manifold. As a corollary, we produce a host of concordance invariants for knots in a general 3-manifold, one such invariant for every non-zero Floer class. We apply our results to produce analogues of the Ozsv\'ath-Szab\'o-Rasmussen concordance invariant for links, allowing us to reprove the link version of the Milnor conjecture, and, furthermore, to show that knot Floer homology detects strongly quasipositive fibered links.