New metric reconstruction scheme for gravitational self-force calculations

TL;DR

This paper introduces a new, more regular gauge-based method for calculating metric perturbations caused by particles orbiting Kerr black holes, which is crucial for modeling gravitational waves from extreme mass ratio inspirals.

Contribution

It develops a Teukolsky puncture scheme using the GHZ formalism, improving gauge regularity and facilitating second-order self-force calculations in Kerr spacetime.

Findings

The GHZ formalism simplifies gauge completion calculations.

The new puncture scheme reduces large cancellations in metric computations.

Demonstrated the scheme in Minkowski spacetime for a static particle.

Abstract

Inspirals of stellar-mass objects into massive black holes will be important sources for the space-based gravitational-wave detector LISA. Modelling these systems requires calculating the metric perturbation due to a point particle orbiting a Kerr black hole. Currently, the linear perturbation is obtained with a metric reconstruction procedure that puts it in a "no-string" radiation gauge which is singular on a surface surrounding the central black hole. Calculating dynamical quantities in this gauge involves a subtle procedure of "gauge completion" as well as cancellations of very large numbers. The singularities in the gauge also lead to pathological field equations at second perturbative order. In this paper we re-analyze the point-particle problem in Kerr using the corrector-field reconstruction formalism of Green, Hollands, and Zimmerman (GHZ). We clarify the relationship between the GHZ formalism and previous reconstruction methods, showing that it provides a simple formula for the "gauge completion". We then use it to develop a new method of computing the metric in a more regular gauge: a Teukolsky puncture scheme. This scheme should ameliorate the problem of large cancellations, and by constructing the linear metric perturbation in a sufficiently regular gauge, it should provide a first step toward second-order self-force calculations in Kerr. Our methods are developed in generality in Kerr, but we illustrate some key ideas and demonstrate our puncture scheme in the simple setting of a static particle in Minkowski spacetime.