No Arabic 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 Poincare 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-analyt
We classify the hypersurfaces of Euclidean space that carry a totally geodesic foliation with complete leaves of codimension one. In particular, we show that rotation hypersurfaces with complete profiles of codimension one are characterized by their warped product structure. The local version of the problem is also considered.
The problem of the existence of an additional (independent on the energy) first integral, of a geodesic (or magnetic geodesic) flow, which is polynomial in momenta is studied. The relation of this problem to the existence of nontrivial solutions of stationary dispersionless limits of two-dimensional soliton equations is demonstrated. The nonexistence of an additional quadratic first integral is established for certain classes of magnetic geodesic flows.
We give a new proof of Moeckels result that for any finite index subgroup of the modular group, almost every real number has its regular continued fraction approximants equidistributed into the cusps of the subgroup according to the weighted cusp widths. Our proof uses a skew product over a cross-section for the geodesic flow on the modular surface. Our techniques show that the same result holds true for approximants found by Nakadas alpha-continued fractions, and also that the analogous result holds for approximants that are algebraic numbers given by any of Rosens lambda-continued fractions, related to the infinite family of Hecke triangle Fuchsian groups.
In this article, we study the ergodicity of the geodesic flows on surfaces with no focal points. Let $M$ be a smooth connected and closed surface equipped with a $C^infty$ Riemannian metric $g$, whose genus $mathfrak{g} geq 2$. Suppose that $(M,g)$ has no focal points. We prove that the geodesic flow on the unit tangent bundle of $M$ is ergodic with respect to the Liouville measure, under the assumption that the set of points on $M$ with negative curvature has at most finitely many connected components.
In this paper we give a complete local parametric classification of the hypersurfaces with dimension at least three of a space form that carry a totally geodesic foliation of codimension one. A classification under the assumption that the leaves of the foliation are complete was given in cite{drt} for Euclidean hypersurfaces. We prove that there exists exactly one further class of local examples in Euclidean space, all of which have rank two. We also extend the classification under the global assumption of completeness of the leaves for hypersurfaces of the sphere and show that there exist plenty of examples in hyperbolic space.