Dimensionally-reduced sutured Floer homology as a string homology

Joint with Eric Schoenfeld.

We show that the sutured Floer homology of a sutured 3-manifold of the form [latex](D^2 \times S^1, F \times S^1)[/latex] can be expressed as the homology of a string-type complex, generated by certain sets of curves on [latex](D^2, F)[/latex] and with a differential given by resolving crossings. We also give some generalisations of this isomorphism, computing “hat” and “infinity” versions of this string homology. In addition to giving interesting elementary facts about the algebra of curves on surfaces, these isomorphisms are inspired by, and establish further, connections between invariants from Floer homology and string topology.

Itsy bitsy topological field theory

We construct an elementary, combinatorial kind of topological quantum field theory, based on curves, surfaces, and orientations. The construction derives from contact invariants in sutured Floer homology and is essentially an elaboration of a TQFT defined by Honda–Kazez–Matic. This topological field theory stores information in binary format on a surface and has “digital” creation and annihilation operators, giving a toy-model embodiment of “it from bit”.

Sutured TQFT, torsion, and tori

We use the theory of sutured TQFT to classify contact elements in the sutured Floer homology, with Z coefficients, of certain sutured manifolds of the form \( (\Sigma \times S^1, F \times S^1) \) where \( \Sigma \) is an annulus or punctured torus. Using this classification, we give a new proof that the contact invariant in sutured Floer homology with Z coefficients of a contact structure with Giroux torsion vanishes. We also give a new proof of Massot’s theorem that the contact invariant vanishes for a contact structure on \( (\Sigma \times S^1, F \times S^1) \) described by an isolating dividing set.