Non hypoellipticité analytique pour des opérateurs à caractéristiques doubles
Non hypoellipticité des opérateurs différentiels du type de Fuchs
Non hypoellipticité d'opérateurs elliptiques singuliers
Nonlinear equations on Carnot groups and curvature problems for CR manifolds
We give a short overview of sub-Laplacians on Carnot groups starting from a result by Caccioppoli dated 1934. Then we show that sub-Laplacians on Carnot groups of step one arise in studying curvature problems for manifolds. We restrict our presentation to the cases of the Webster-Tanaka curvature problem for the sphere and of the Levi-curvature equation for strictly pseudoconvex functions.