On the existence of parallel one forms

Abstract

In this paper, using the Finslerian settings, we study the existence of parallel one forms (or, equivalently parallel vector fields) on a Riemannian manifold. We show that a parallel one form on a Riemannian manifold M is a holonomy invariant function on the tangent bundle TM with respect to the geodesic spray. We prove that if the metrizability freedom of the geodesic spray of (M, F) is 1, then the (M, F) does not admit a parallel one form. We investigate a sufficient condition on a Riemannian manifold to admit a parallel one form. As by-product, we relate the existence of a proper affine Killing vector field by the metrizability freedom. We establish sufficient conditions for the existence of a parallel one form on a Finsler manifold. By counter-examples, we show that if the metrizability freedom is greater than 1, then the manifold (Riemannian or Finslerian) does not necessarily admit a parallel one form. Various special cases and examples are studied and discussed.