Regularity of quasi-linear equations with Hörmander vector fields of step two

Giovanna Citti, Shirsho Mukherjee

If the smooth vector fields $X_1,\dots ,X_m$ and their commutators span the tangent space at every point in $\Omega \subseteq {\mathbb{R}}^N$ for any fixed $m\le N$, then we establish the…