Weak Finsler Strutures and the Funk Metric

导航问题的几何：$\lambda-$Funk芬斯勒度量

Geometry of a Navigation problem: The $λ-$Funk Finsler Metrics

该研究从几何角度分析受对称风流扰动的湖泊导航行进时间问题，推导得到推广欧氏度量与Funk度量的Randers度量，并给出点到点、点到线等场景的距离/行进时间公式。

Harmonic symmetrization of convex sets and of Finsler structures, with applications to Hilbert geometry

David Hilbert discovered in 1895 an important metric that is canonically associated to any convex domain $Ω$ in the Euclidean (or projective) space. This metric is known to be Finslerian, and the usual proof assumes a certain degree of smoothness of the boundary of $Ω$ and refers to a theorem by Busemann and Mayer that produces the norm of a tangent vector from the distance function. In this paper, we develop a new approach for the study of the Hilbert metric where no differentiability is assumed. The approach exhibits the Hilbert metric on a domain as a symmetrization of a natural weak metric…

Funk functions and projective deformations of sprays and Finsler spaces of scalar flag curvature

In 2001, Zhongmin Shen asked if it is possible for two projectively related Finsler metrics to have the same Riemann curvature tensor, [14, page 184]. In this paper, we provide an answer to this question, within the class of Finsler metrics of scalar flag curvature. In Theorem 3.1, we show that the answer is negative, for non-vanishing scalar flag curvature. The answer is known to be positive when the scalar flag curvature vanishes, [12, 14] and this positive answer is related to the existence of many solutions to Hilbert's Fourth Problem. As a generalisation of this problem, we can ask if it …

关于Finsler度量族的研究

On families of Finsler metrics

本文针对非对称Finsler度量引入两类度量族，系统研究其测地线、完备性及单位球形状等性质，并应用于Funk几何、Hilbert几何和Teichmüller空间中的Thurston型非对称度量。

Analytic properties and the asymptotic behavior of the area function of a Funk metric

In Minkowski geometry the unit ball is a compact convex body $K$ containing the origin in its interior. The boundary of the body is formed by the unit vectors. We also have a so-called Minkowski functional to measure the length of vectors. By changing the origin in the interior of the body we have a smoothly varying family of Minkowski functionals. This is called the Funk metric. Under some regularity conditions the Minkowski functionals allow us to measure the volume (area) of the indicatrix bodies (hypersurfaces). Some homogenity properties provide the volume and the area to be proportional.…

Finsler Metrics with K=0 and S=0

In Finsler geometry, there are infinitely many models of constant curvature. The Funk metrics, the Hilbert-Klein metrics and the Bryant metrics are projectively flat with non-zero constant curvature. A recent example constructed by the author is projectively flat with zero curvature. In this paper, we introduce a technique to construct non-projectively flat Finsler metrics with zero curvature in each dimension. The technique can be used to construct many non-projectively flat Finsler metrics of constant curvature.

Rigidity results for geodesically reversible Finsler metrics

A Finsler metric is geodesically reversible if geodesics remain geodesics after a change of orientation. Asymmetric norms on vector spaces and Funk metrics in the interior of convex bodies are examples of geodesically reversible metrics that are not necessarily sums of reversible metrics and closed 1-forms. However, there seem to be few such examples in closed manifolds. In this paper the theory of volumes and areas on Finsler spaces is applied to establish a number of rigidity theorems which partially explain this paucity of examples. These rigidity results settle some hitherto unsolved cases…

Asymmetry in Hilbert's fourth problem

In the asymmetric setting, Hilbert's fourth problem asks to construct and study all (non-reversible) projective Finsler metrics: Finsler metrics defined on open, convex subsets of real projective $n$-space for which geodesics lie on projective lines. While asymmetric norms and Funk metrics provide many examples of essentially non-reversible projective metrics defined on proper convex subsets of projective $n$-space, it is shown that any projective Finsler metric defined on the whole projective $n$-space is the sum of a reversible projective metric and an exact 1-form.

Three isometrically equivalent models of the Finsler-Poincaré disk

We present the isometry between the 2-dimensional Funk model and the Finsler-Poincaré disk. Then, we introduce the Finslerian Poincaré upper half plane model, which turns out to be also isometrically equivalent to the previous models. As application, we state the gapless character of the first eigenvalue for the aforementioned three spaces.

Sprays on Hamel-Funk Functions Model

Hamel functions of a spray play an important role in the study of the projective metrizability of the concerned spray, and Funk functions are special Hamel functions. A Finsler metric is a special Hamel function of the spray induced by the metric itself and a Funk metric is a special Funk function of a Minkowski spray. In this paper, we study sprays on a Hamel or Funk function model. Firstly, we give some basic properties of a Hamel or Funk function of a spray and some curvature properties of a Hamel or Funk function in projective relations. We use the Funk metric to construct a family of spra…

On Finsler surfaces of constant flag curvature with a Killing field

We study two-dimensional Finsler metrics of constant flag curvature and show that such Finsler metrics that admit a Killing field can be written in a normal form that depends on two arbitrary functions of one variable. Furthermore, we find an approach to calculate these functions for spherically symmetric Finsler surfaces of constant flag curvature. In particular, we obtain the normal form of the Funk metric on the unit disk D^2.

Isoparametric hypersurfaces induced by navigation in Lorentz Finsler geometry

Using a navigation process with the datum $(F,V)$, in which $F$ is a Finsler metric and the smooth tangent vector field $V$ satisfies $F(-V(x))>1$ everywhere, a Lorentz Finsler metric $\tilde{F}$ can be induced. Isoparametric functions and isoparametric hypersurfaces with or without involving a smooth measure can be defined for $\tilde{F}$. When the vector field $V$ in the navigation datum is homothetic, we prove the local correspondences between isoparametric functions and isoparametric hypersurfaces before and after this navigation process. Using these correspondences, we provide some exampl…

Convex bodies in Euclidean and Weil-Petersson geometries

On a convex body in a Euclidean space, we introduce a new variational formulation for its Funk metric, a Finsler metric compatible with the tautological Finsler structure of the convex body. We generalize the metric on Teichmuller spaces with the Weil-Petersson distance function. A set of similarities the resulting metric structure shares with Thurston's asymmetric metric is noted.

常曲率球对称射影 Finsler 度量的完整群

The holonomy of spherically symmetric projective Finsler metrics of constant curvature

本文证明常曲率球对称射影 Finsler 度量的完整群极大，并在单连通情形下同构于 $Diff_o({\mathbb S^{n-1}})$，首次显式刻画了非 Berwald 的 n 维 Finsler 流形完整群。

非对称度量空间中的梯度流及其应用

Gradient flows in asymmetric metric spaces and applications

该研究通过离散逼近方法探究非对称度量空间中的梯度流，证明最大斜率曲线的存在性，引入$(p,λ)$-凸性得到其渐近行为的正则化效应，并给出在Finsler流形、无穷维Funk空间及紧Finsler流形热流中的应用。