On the unreasonable effectiveness of the post-Newtonian approximation in gravitational physics

TL;DR

The paper discusses the surprising effectiveness of the post-Newtonian approximation in modeling strong-field gravitational systems, which is crucial for gravitational-wave detection, despite its theoretical limitations.

Contribution

It explores the reasons behind the post-Newtonian approximation's success in strong-field regimes and highlights its importance in gravitational-wave astronomy.

Findings

Effective in describing binary pulsars and black hole inspirals

Crucial for gravitational-wave signal predictions

Effectiveness remains largely unexplained

Abstract

The post-Newtonian approximation is a method for solving Einstein's field equations for physical systems in which motions are slow compared to the speed of light and where gravitational fields are weak. Yet it has proven to be remarkably effective in describing certain strong-field, fast-motion systems, including binary pulsars containing dense neutron stars and binary black hole systems inspiraling toward a final merger. The reasons for this effectiveness are largely unknown. When carried to high orders in the post-Newtonian sequence, predictions for the gravitational-wave signal from inspiraling compact binaries will play a key role in gravitational-wave detection by laser-interferometric observatories.