Pseudo-Riemannian metrics on closed surfaces whose geodesic flows admit nontrivial integrals quadratic in momenta, and proof of the projective Obata conjecture for two-dimensional pseudo-Riemannian metrics

We describe all pseudo-Riemannian metrics on closed surfaces whose geodesic flows admit nontrivial integrals quadratic in momenta. As an application, we solve the Beltrami problem on closed surfaces, prove the nonexistence of quadratically-superintegrable metrics of nonconstant curvature on closed surfaces, and prove the two-dimensional pseudo-Riemannian version of the projective Obata conjecture.Comment: 33 pages, 7 pictures. This paper replaces arXiv:0911.3521v1 and arXiv:1002.013

There exist no locally symmetric Finsler spaces of positive or negative flag curvature

We show that the results of Foulon (1997 an 2002) and Kim (2007) (independently, Deng and Hou (2007)) about the nonexistence of locally symmetric Finsler metrics of positive or negative flag curvature are in fact local

Strictly non-proportional geodesically equivalent metrics have htop(g)=0h_\text{top}(g)=0

Suppose the Riemannian metrics $g$ and $\bar g$ on a closed connected manifold $M^n$ are geodesically equivalent and strictly non-proportional at least at one point. Then the topological entropy of the geodesic flow of $g$ vanishes.Comment: This is a slightly extended version of the paper submitted to ETDS. 16 pages, one .eps figur

The Myers-Steenrod theorem for Finsler manifolds of low regularity

We prove a version of Myers-Steenrod's theorem for Finsler manifolds under minimal regularity hypothesis. In particular we show that an isometry between $C^{k,\alpha}$-smooth (or partially smooth) Finsler metrics, with $k+\alpha>0$, $k\in \mathbb{N} \cup \{0\}$, and $0 \leq \alpha \leq 1$ is necessary a diffeomorphism of class $C^{k+1,\alpha}$. A generalisation of this result to the case of Finsler 1-quasiconformal mapping is given. The proofs are based on the reduction of the Finlserian problems to Riemannian ones with the help of the the Binet-Legendre metric.Comment: 14 page

Completeness and incompleteness of the Binet-Legendre Metric

The goal of this short paper is to give condition for the completeness of the Binet-Legendre metric in Finsler geometry. The case of the Funk and Hilbert metrics in a convex domain are discussed.Comment: 17 pages, 3 figure

A counterexample to Belgun-Moroianu conjecture

We construct an example of a closed manifold with a nonflat reducible locally metric connection such that it preserves a conformal structure and such that it is not the Levi-Civita connection of a Riemannian metric.Comment: are as always welcom