On the Legendrian realisation of parametric families of knots

Abstract

We study the natural inclusion of the space of Legendrian embeddings in $(\mathbb{S}^3,\xi_{\operatorname{std}})$ into the space of smooth embeddings from a homotopical viewpoint. T. K\'alm\'an posed in [Kal] the open question of whether for every fixed knot type $\mathcal{K}$ and Legendrian representative $\mathcal{L}$, the homomorphism $\pi_1(\mathcal{L})\to\pi_1(\mathcal{K})$ is surjective. We positively answer this question for infinitely many knot types $\mathcal{K}$ in the three main families (hyperbolic, torus and satellites) and every stabilised Legendrian representative in $(\mathbb{S}^3,\xi_{\operatorname{std}})$. We then show that for every $n\geq 3$, the homomorphisms $\pi_n(\mathcal{L})\to\pi_n(\mathcal{K})$ and $\pi_n(\mathcal{FL})\to\pi_n(\mathcal{K})$ are never surjective for any knot type $\mathcal K$, Legendrian representative $\mathcal L$ or formal Legendrian representative $\mathcal{FL}$. This shows the existence of rigidity at every higher-homotopy level beyond $\pi_3$. For completeness, we also show that surjectivity at the $\pi_2$-level depends on the smooth knot type.