Radio Pulsars as a Laboratory for Strong-field Gravity Tests

Lijing Shao

Submitted on 30 June 2022


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.


Comment: 16 pages, 4 figures; Invited contribution to the forthcoming book "Modified and Quantum Gravity - From theory to experimental searches on all scales", Springer Nature, (Eds) Claus L\"ammerzahl and Christian Pfeifer

Subjects: General Relativity and Quantum Cosmology; Astrophysics - High Energy Astrophysical Phenomena