Guts of nearly fibered knots

Abstract

The guts of a knot is an invariant defined for the knot complement by Agol-Zhang. Nearly fibered knots, which are defined as knots whose Floer homology has dimension two in the top Alexander grading, were introduced by Baldwin-Sivek. In this note, we provide three models for the guts of nearly fibered knots in the $3$-sphere. As a corollary, the nearly fibered condition can be purely topologically characterized and is independent of the specific version of Floer theory.

v3, 8 pages: accepted version, to appear in Algebraic Geometry & Topology; comments are welcome