A completely integrable flow of star-shaped curves on the light cone in Lorentzian ${\mathbb{R}}^4$

In this paper we prove that the space of differential invariants for curves with arc-length parameter in the light cone of Lorentzian ${\mathbb{R}}^4$, invariants under the centro-affine action of the Lorentzian group, is Poisson equivalent to the space of conformal differential invariants for curves in the M"obius sphere. We use this relation to find realizations of solutions of a complexly coupled system of KdV equations as flows of curves in the cone.