Radio Pulsars as a Laboratory for Strong-field Gravity Tests

TL;DR

Radio pulsars serve as precise natural laboratories for testing strong-field gravity theories, complementing traditional tests of general relativity, especially with upcoming advanced radio telescopes.

Contribution

This paper reviews how radio pulsars are used to test strong-field gravity, highlighting recent examples and future prospects with new radio telescope technology.

Findings

Radio pulsar timing constrains alternative gravity theories.

Tests of gravitational dipolar radiation and massive gravity.

Future telescopes will enhance strong gravity tests.

Abstract

General relativity offers a classical description to gravitation and spacetime, and is a cornerstone for modern physics. It has passed a number of empirical tests with flying colours, mostly in the weak-gravity regimes, but nowadays also in the strong-gravity regimes. Radio pulsars provide one of the earliest extrasolar laboratories for gravity tests. They, in possession of strongly self-gravitating bodies, i.e. neutron stars, are playing a unique role in the studies of strong-field gravity. Radio timing of binary pulsars enables very precise measurements of system parameters, and the pulsar timing technology is extremely sensitive to various types of changes in the orbital dynamics. If an alternative gravity theory causes modifications to binary orbital evolution with respect to general relativity, the theory prediction can be confronted with timing results. In this chapter, we review the basic concepts in using radio pulsars for strong-field gravity tests, with the aid of some recent examples in this regard, including tests of gravitational dipolar radiation, massive gravity theories, and the strong equivalence principle. With more sensitive radio telescopes coming online, pulsars are to provide even more dedicated tests of strong gravity in the near future.