A spectral condition for the control of eigenfunctions of Baouendi-Grushin type operators

We study a concentration inequality for eigenfunctions of a Baouendi-Grushin operator on a cylinder or a torus. Using separation of variables, we prove that this inequality holds under a spectral multiplicity condition. Using Albert-Uhlenbeck’s theory, we then prove that this spectral condition is generically true for such sub-elliptic operators.