Koszul dual $\mathcal{A}_{\infty}$ algebras for star-shaped diagrams -- Part 1
Isabella Khan
TL;DR
This work develops a Koszul dual framework for star-shaped diagrams in bordered Heegaard Floer theory by constructing weighted $\mathcal{A}_{\infty}$-algebras $\mathcal{A}$ and $\mathcal{B}$ from horizontal star-shaped slices and defining dualizing $AA$- and $DD$-bimodules. It introduces a graphical calculus for $\mathcal{A}_{\infty}$-operations, builds diagonals to define tensor-product $\mathcal{A}_{\infty}$-structures, and computes explicit structures for the $\alpha$-bordered algebra $\mathcal{A}$ and the $\beta$-bordered algebra $\mathcal{B}$, including gradings and higher multiplications. The paper proves that these algebras admit valid higher operations and dualizing bimodules, laying the groundwork for a Koszul duality result that will be completed in Part 2. Together, these constructions enable the computation of Heegaard Floer invariants via tensor products of bordered pieces, connecting to broader frameworks such as the fully wrapped Fukaya category. The results provide concrete, combinatorial models for weighted $\mathcal{A}_{\infty}$-structures with both operationally bounded and unbounded features, and establish a robust algebraic path toward dual decompositions of bordered Heegaard Floer data.
Abstract
By slicing the Heegaard diagram for a given $3$-manifold in a particular way, it is possible to construct $\mathcal{A}_{\infty}$-bimodules, the tensor product of which retrieves the Heegaard Floer homology of the original 3-manifold. The first step in this is to construct algebras corresponding to the individual slices. Here, we use the graphical calculus for $\mathcal{A}_{\infty}$-structures introduced by Lipshitz, Ozsváth, and Thurston, to construct Koszul dual weighted $\mathcal{A}_{\infty}$-algebras $\mathcal{A}$ and $\mathcal{B}$, and dualizing bimodules for a particular star-shaped class of slice. The duality result is then proved in the sequel.
