Spin-geodesic deviations in the Kerr spacetime

TL;DR

This paper studies how small spinning bodies deviate from geodesic paths in Kerr spacetime, extending previous work to more general trajectories by linearizing the equations in spin and deviation variables.

Contribution

It generalizes previous analyses by deriving deviations from geodesics for spinning bodies in Kerr spacetime beyond equatorial circular orbits.

Findings

Derived linearized deviation equations for spinning bodies in Kerr spacetime.

Extended previous results to generic geodesic trajectories.

Provided analytical framework for small spin deviations from geodesic motion.

Abstract

The dynamics of extended spinning bodies in the Kerr spacetime is investigated in the pole-dipole particle approximation and under the assumption that the spin-curvature force only slightly deviates the particle from a geodesic path. The spin parameter is thus assumed to be very small and the back reaction on the spacetime geometry neglected. This approach naturally leads to solve the Mathisson-Papapetrou-Dixon equations linearized in the spin variables as well as in the deviation vector, with the same initial conditions as for geodesic motion. General deviations from generic geodesic motion are studied, generalizing previous results limited to the very special case of an equatorial circular geodesic as the reference path.