The contact Banach-Mazur distance and large scale geometry of overtwisted contact forms

TL;DR

This paper introduces a new, less restrictive contact distance measure and demonstrates how overtwisted contact structures' vanishing contact homology enables embedding parts of Euclidean space into their moduli space.

Contribution

It defines a novel contact distance that extends previous work and leverages contact homology properties to embed Euclidean space into the space of overtwisted contact forms.

Findings

Defined a less restrictive contact distance.

Used contact homology vanishing to embed Euclidean space.

Analyzed large-scale geometry of overtwisted contact forms.

Abstract

In the symplectic realm, a distance between open starshaped domains in Liouville manifolds was recently defined. This is the symplectic Banach-Mazur distance. It was proposed by Ostrover and Polterovich and developed by Ostrover, Polterovich, Usher, Gutt, Zhang and Stojisavljevi\'c. The natural question is, can an analogous distance in the contact realm be defined? One idea is to define the distance on contact hypersurfaces of Liouville manifolds and another one on contact forms supporting isomorphic contact structures. Rosen and Zhang recently defined such a distance working with manifolds that are prequantizations of Liouville manifolds. They also considered a distance on contact forms supporting the same contact structure on a contact manifold $Y$. This allowed them to view the space of contact forms supporting isomorphic contact structures on a manifold $Y$ as a pseudometric space, study its properties, and derive interesting results. In this work, we do something similar, yet the distance we define is less restrictive. Moreover, viewing contact homology algebra as a persistence module, focusing purely on the overtwisted case and exploiting the fact that the contact homology of overtwisted contact structures vanishes, allows us to bi-Lipschitz embed part of the 2-dimensional Euclidean space into the space of overtwisted contact forms supporting a given contact structure on a smooth closed manifold $Y$.