Global Fukaya category II: applications

TL;DR

This paper demonstrates the non-triviality of a bundle of $A_ _{ fty}$ categories over a manifold, revealing new geometric phenomena and linking Floer theory to algebraic K-theory and number theory.

Contribution

It shows the bundle's non-triviality through a sample computation and uncovers new curvature phenomena for $ ext{PU}(2)$ and $ ext{Ham}(S^2)$ connections, connecting Floer theory to algebraic K-theory.

Findings

The bundle of $A_ _{ fty}$ categories is generally non-trivial.

New curvature phenomena for $ ext{PU}(2)$ and $ ext{Ham}(S^2)$ connections.

Categorified algebraic K-theory admits a $ ext{Z}$ injection in degree 4.

Abstract

To paraphrase, part I constructs a bundle of $A _{\infty}$ categories given the input of a Hamiltonian fibration over a smooth manifold. Here we show that this bundle is generally non-trivial by a sample computation. One principal application is differential geometric, and the other is about algebraic $K$-theory of the integers and the rationals. We find new curvature constraint phenomena for smooth and singular $\mathcal{G}$-connections on principal $\mathcal{G}$-bundles over $S ^{4}$, where $\mathcal{G}$ is $\operatorname {PU} (2)$ or $\operatorname {Ham} (S ^{2} )$. Even for the classical group $\operatorname {PU} (2)$ these phenomena are inaccessible to known techniques like the Yang-Mills theory. The above mentioned computation is the geometric component used to show that the categorified algebraic $K$-theory of the integers and the rationals, defined in ~\cite{cite_SavelyevAlgKtheory} following To\"en, admits a $\mathbb{Z} $ injection in degree $4$. This gives a path from Floer theory to number theory.