This article is concerned with the geometry of germs of real analytic surfaces in $(\mathbb{ C}^2,0)$ having an isolated Cauchy-Riemann (CR) singularity at the origin. These are perturbations of { \it Bishop quadrics}. There are two kinds of CR singularities stable under perturbation~: { \it elliptic} and { \it hyperbolic}. Elliptic case was studied by Moser-Webster \cite{ moser-webster} who showed that such a surface is locally, near the CR singularity, holomorphically equivalent to { \it normal form} from which lots of geometric features can be read off. In this article we focus on perturbations of { \it hyperbolic} quadrics. As was shown by Moser-Webster \cite{ moser-webster}, such a surface can be transformed to a formal { \it normal form} by a formal change of coordinates that may not be holomorphic in any neighborhood of the origin. Given a { \it non-degenerate} real analytic surface $M$ in $(\mathbb{ C}^2,0)$ having a { \it hyperbolic} CR singularity at the origin, we prove the existence of a non-constant Whitney smooth family of connected holomorphic curves intersecting $M$ along holomorphic hyperbolas. This is the very first result concerning hyperbolic CR singularity not equivalent to quadrics. This is a consequence of a non-standard KAM-like theorem for pair of germs of holomorphic involutions $\{ \tau_1,\tau_2\}$ at the origin, a common fixed point. We show that such a pair has large amount of invariant analytic sets biholomorphic to $\{ z_1z_2=const\}$ (which is not a torus) in a neighborhood of the origin, and that they are conjugate to restrictions of linear maps on such invariant sets.
Categories: math.CV math.DS