The Lagrangian equations of motion for massive spinning test particles (tops)
moving on a gravitational background using General Relativity are presented.
The paths followed by tops are nongeodesic. An exact solution for the motion of
tops on a Schwarzschild background which allows for superluminal propagation of
tops is studied. It is shown that the solution becomes relevant for particles
with small masses, such as neutrinos. This general result is used to calculate
the necessary condition to produce superluminal motion in part of the
trajectory of a small mass particle in a weak gravitational field. The
condition for superluminal motion establishes a relation between the mass,
energy and total angular momentum of the particle.Comment: 7 pages, accepted in Class. Quantum Gra
