Multiparameter tests of general relativity using multiband gravitational-wave observations

TL;DR

Multiband gravitational-wave observations combining 3G ground-based detectors and LISA can precisely measure post-Newtonian coefficients, enabling stringent tests of general relativity and constraining alternative gravity theories.

Contribution

This work demonstrates that multiband observations can measure PN coefficients with unprecedented accuracy, surpassing previous bounds from single-band detections.

Findings

Most PN phasing coefficients measured below a few percent accuracy

Multiband bounds outperform single-band bounds by two orders of magnitude

Enhanced constraints on modified theories of gravity

Abstract

In this Letter we show that multiband observations of stellar-mass binary black holes by the next generation of ground-based observatories (3G) and the space-based Laser Interferometer Space Antenna (LISA) would facilitate a comprehensive test of general relativity by simultaneously measuring all the post-Newtonian (PN) coefficients. Multiband observations would measure most of the known PN phasing coefficients to an accuracy below a few percent---two orders-of-magnitude better than the best bounds achievable from even `golden' binaries in the 3G or LISA bands. Such multiparameter bounds would play a pivotal role in constraining the parameter space of modified theories of gravity beyond general relativity.