Influence of internal structure on the motion of test bodies in extreme mass ratio situations

TL;DR

This paper studies how the internal structure of test bodies, including spin and tidal effects, influences their motion in strong gravitational fields, with implications for gravitational wave detection.

Contribution

It derives equations of motion for structured bodies up to quadrupolar order in Kerr spacetime and compares results with self-force calculations in extreme mass ratio scenarios.

Findings

Motion characterized by effective potential and binding energy.

Internal structure significantly affects test body trajectories.

Results have potential implications for gravitational wave modeling.

Abstract

We investigate the motion of test bodies with internal structure in General Relativity. With the help of a multipolar approximation method for extended test bodies we derive the equations of motion up to the quadrupolar order. The motion of pole-dipole and quadrupole test bodies is studied in the context of the Kerr geometry. For an explicit quadrupole model, which includes spin and tidal interactions, the motion in the equatorial plane is characterized by an effective potential and by the binding energy. We compare our findings to recent results for the conservative part of the self-force of bodies in extreme mass ratio situations. Possible implications for gravitational wave physics are outlined.