# Self-force correction to geodetic spin precession in Kerr spacetime

## TL;DR

This paper derives a gauge-invariant expression for the gravitational self-force correction to the geodetic spin precession of a small spinning object in a bound orbit around a Kerr black hole, extending previous results to Kerr spacetime.

## Contribution

It generalizes the self-force correction to spin precession from Schwarzschild to Kerr spacetime, providing a gauge-invariant formulation suitable for numerical and analytical computations.

## Key findings

- Derived an expression for $ riangle\psi$ in Kerr spacetime.
- Showed the zero-eccentricity limit differs from circular-orbit results by a gauge-invariant term.
- Facilitates future self-force calculations for eccentric orbits in Kerr geometry.

## Abstract

We present an expression for the gravitational self-force correction to the geodetic spin precession of a spinning compact object with small, but non-negligible mass in a bound, equatorial orbit around a Kerr black hole. We consider only conservative back-reaction effects due to the mass of the compact object ($m_1$) thus neglecting the effects of its spin $s_1$ on its motion, i.e, we impose $s_1 \ll G m_1^2/c$ and $m_1 \ll m_2$, where $m_2$ is the mass parameter of the background Kerr spacetime. We encapsulate the correction to the spin precession in $\psi$, the ratio of the accumulated spin-precession angle to the total azimuthal angle over one radial orbit in the equatorial plane. Our formulation considers the gauge-invariant $\ord(m_1)$ part of the correction to $\psi$, denoted by $\Delta\psi$, and is a generalization of the results of [Class. Quan. Grav., 34, 084001 (2017)] to Kerr spacetime. Additionally, we compute the zero-eccentricity limit of $\Delta\psi$ and show that this quantity differs from the circular-orbit $\Delta\psi^\text{circ}$ by a gauge-invariant quantity containing the gravitational self-force correction to general relativistic periapsis advance in Kerr spacetime. Our result for $\Delta\psi$ is expressed in a manner that readily accommodates numerical/analytical self-force computations, e.g., in radiation gauge, and paves the way for the computation of a new eccentric-orbit Kerr gauge invariant beyond the generalized redshift.