Influence of internal structure on the motion of test bodies in extreme mass ratio situations (MG13)

TL;DR

This paper investigates how the internal structure of extended test bodies, including quadrupole moments, affects their motion in Kerr spacetime, using a multipolar approximation and comparing with self-force results.

Contribution

It introduces a multipolar approximation scheme with an explicit quadrupole model inspired by post-Newtonian effective actions for analyzing test body motion in Kerr geometry.

Findings

Effective potential characterizes motion in Kerr spacetime.

Comparison with self-force results validates the model.

Internal structure influences test body trajectories.

Abstract

We present some recent results on the motion of test bodies with internal structure in General Relativity. On the basis of a multipolar approximation scheme, we study the motion of extended test bodies endowed with an explicit model for the quadrupole. The model is inspired by effective actions recently proposed in the context of the post-Newtonian approximation, including spin-squared and tidal contributions. In the equatorial plane of the Kerr geometry, the motion can be characterized by an effective potential of the binding energy. We compare our findings to recent results for the conservative part of the self-force in astrophysically realistic situations.