Generic Properties of Geodesic Flows on Analytic Hypersurfaces of Euclidean Space (1908.04662v3)

Abstract: Consider the geodesic flow on a real-analytic closed hypersurface $M$ of $\mathbb{R}^n$, equipped with the standard Euclidean metric. The flow is entirely determined by the manifold and the Riemannian metric. Typically, geodesic flows are perturbed by varying the metric. In the present paper, however, only the Euclidean metric is used, and instead the manifold $M$ is perturbed. In this context, analogues of the following theorems are proved: the bumpy metric theorem; a theorem of Klingenberg and Takens regarding generic properties of $k$-jets of Poincar\'e maps along geodesics; and the Kupka-Smale theorem. Moreover, the proofs presented here are valid in the real-analytic topology. Together, these results imply the following two main theorems: if $M$ is a real-analytic closed hypersurface in $\mathbb{R}^n$ (with $n \geq 3$) on which the geodesic flow with respect to the Euclidean metric has a nonhyperbolic periodic orbit, then $C^{\omega}$-generically the geodesic flow on $M$ with respect to the Euclidean metric has a hyperbolic periodic orbit with a transverse homoclinic orbit; and there is a $C^{\omega}$-open and dense set of real-analytic, closed, and strictly convex surfaces $M$ in $\mathbb{R}^3$ on which the geodesic flow with respect to the Euclidean metric has a hyperbolic periodic orbit with a transverse homoclinic orbit. The methods used here also apply to the classical setting of perturbations of metrics on a Riemannian manifold to obtain real-analytic versions of these theorems in that case. These are among the first perturbation-theoretic results for real-analytic geodesic flows.