Third-order affine-invariant (systems of) PDEs in two independent variables as vanishing of the Fubini-Pick invariant

Dmitri Alekseevsky, Gianni Manno, Giovanni Moreno

In this paper we study $3^{\mathrm{rd}}$ order (system of) PDEs in two independent variables $x,y$ and one unknown function $u$ that are invariant with respect to the group of affi…