Harnack inequality for hypoelliptic second order partial differential operators

Alessia E. Kogoj, Sergio Polidoro

We consider nonnegative solutions $u:\Omega ⟶\mathbb{R}$ of second order hypoelliptic equations \begin{equation*} \mathscr{L} u(x) =\sum_{i,j=1}^n \partial_{x_i} \left(a_{…