A generalization and short proof of a theorem of Hano on affine vector fields

We prove that a bounded affine vector field on a complete Finsler manifold is a Killing vector field. This generalizes the analogous result of Hano for Riemannian manifolds. Even though our result is more general, the proof is significantly simpler.Comment: 3 page

Several Ways to a Berwald Maniflod - and Some Steps Beyond

After summarizing some necessary preliminaries and tools, including Berwald derivative and Lie derivative in pull-back formalism, we present several equivalent conditions, each of which characterizes Berwald manifolds among Finsler manifolds. These range from Berwald’s classical definition to the existence of a torsion-free covariant derivative on the base manifold compatible with the Finsler function, the vanishing of the h-Berwald differential of the Cartan tensor and Aikou’s characterization of Berwald manifolds. Finally, we study some implications of V. Matveev’s observation according to which quadratic convexity may be omitted from the definition of a Berwald manifold. These include, among others, a generalization of Z.I. Szab´o’s well-known metrization theorem, and also lead to a natural generalization of Berwald manifolds, to Berwald { Matveev manifolds.The first two authors were supported by Hungarian Scientific Research Fund OTKA No. NK 81402.peerReviewe