There are non homotopic framed homotopies of long knots

TL;DR

This paper constructs a nontrivial cohomology class in the space of long knots, showing the existence of non-contractible loops of knots that involve crossing changes, and conjectures a new polynomial invariant for certain knots.

Contribution

It introduces a new cohomology class in the essential diagram space of long knots, revealing nontrivial loops involving crossing changes and proposing a novel knot polynomial for unknotting number one knots.

Findings

Existence of non-contractible loops in the essential diagram space

Construction of a new cohomology class extending the Kauffman bracket

Conjecture of a new knot polynomial for knots with unknotting number one

Abstract

Let $\mathcal {M}$ be the space of all, including singular, long knots in 3-space and for which a fixed projection into the plane is an immersion. Let $cl(\Sigma^{(1)}_{iness})$ be the closure of the union of all singular knots in $\mathcal {M}$ with exactly one ordinary double point and such that the two resolutions represent the same (non singular) knot type. We call $\Sigma^{(1)}_{iness}$ the {\em inessential walls} and we call $\mathcal {M}_{ess} = \mathcal {M} \setminus cl(\Sigma^{(1)}_{iness})$ the {\em essential diagram space}. We construct a non trivial class in $H^1(\mathcal {M}_{ess}; \mathbb{Z}[A, A^{-1}])$ by an extension of the Kauffman bracket. This implies in particular that there are loops in $\mathcal {M}_{ess}$ which consist of regular isotopies of knots together with crossing changings and which are not contractible in $\mathcal {M}_{ess}$ (leading to the title of the paper). We conjecture that our construction gives rise to a new knot polynomial for knots of unknotting number one.