Detecting Heegaard Floer homology solid tori
Akram Alishahi, Tye Lidman, Robert Lipshitz
TL;DR
The paper establishes a sharp geometric criterion for Heegaard Floer homology solid tori (HFSTs): a rational homology solid torus $M$ is an HFST iff the Dehn filling along its rational longitude, $M(\lambda)$, contains a non-separating $S^2$. It leverages both the classical bordered Floer framework and the immersed-curve reformulation to relate HFSTs to twisted surgery data and to show that all HFSTs arise as knot complements in reducible manifolds. It then classifies Seifert-fibered HFSTs, showing they occur precisely when the base orbifold is a Möbius band or when the filled space is $D^2(0;p/q,-p/q)$. The results connect bordered Floer theory, twisted coefficients, and immersed-curve techniques to provide a complete picture of HFSTs and their Seifert-fibered instances, with implications for L-space fillings and non-separating sphere phenomena.
Abstract
We show that a rational homology solid torus is a Heegaard Floer homology solid torus if and only if it has a Dehn filling with a non-separating 2-sphere. Using this, we characterize Seifert fibered Heegaard Floer solid tori.
