On Legendrian curves in $\mathbb P^3$

Abstract

We show that if a smooth projective curve $C\subset\mathbb P^3$ (over an algebraically closed field of characteristic zero) is Legendrian with respect to a contact structure (it is well known that a contact structure on $\mathbb P^3$ is unique up to a linear automorphism) and $C$ is linearly normal (i.e., not an isomorphic linear projection of a smooth curve $C'\subset\mathbb P^n$, $n>3$, where $C'$ does not lie in a hyperplane) then $C$ is a twisted cubic or a line.