On the tensorial properties of the generalized Jacobi equation
  The generalized Jacobi equation is a differential equation in local coordinates that describes the behavior of infinitesimally close geodesics with an arbitrary relative velocity. In this note we study some transformation properties for solutions to this equation. We prove two results. First, under any affine coordinate changes we show that the tensor transformation rule maps solutions to solutions. As a consequence, the generalized Jacobi equation is a tensor equation when restricted to suitable Fermi coordinate systems along a geodesic. Second, in dimensions n\ge 3, we explicitly show that the transformation rule does not in general preserve solutions to the generalized Jacobi equation. 
Matias F. Dahl and Ricardo Gallego Torrom\'e
math-ph gr-qc math.MP