Mathematical Research Letters

Volume 28 (2021)

Number 4

Instanton and the depth of taut foliations

Pages: 1197 – 1215



Zhenkun Li (Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Mass., U.S.A.)


Sutured instanton Floer homology was introduced by Kronheimer and Mrowka in [8]. In this paper, we prove that for a taut balanced sutured manifold with vanishing second homology, the dimension of the sutured instanton Floer homology provides a bound on the minimal depth of all possible taut foliations on that balanced sutured manifold. The same argument can be adapted to the monopole and also the Heegaard Floer settings, which gives a partial answer to one of Juhasz’s conjectures in [5]. Also, using the nature of instanton Floer homology, on knot complements, we can construct a taut foliation with bounded depth, given some information on the representation varieties of the knot fundamental groups. This indicates a mystery relation between the representation varieties and some small depth taut foliations on knot complements and gives a partial answer to one of Kronheimer and Mrowka’s conjecture in [8].

This material is based upon work supported by the National Science Foundation under Grant No. 1808794.

Received 30 April 2020

Accepted 2 August 2020

Published 22 November 2021