Will Einstein Have the Last Word on Gravity?

TL;DR

This paper discusses how the LISA gravitational wave observatory could test the validity of Einstein's theory of gravity by observing signals from black hole binaries in the milliHertz frequency band, potentially revealing deviations or extensions of general relativity.

Contribution

It highlights the unique potential of LISA to perform clean, high signal-to-noise tests of gravity theories using gravitational waves from black hole systems.

Findings

LISA can test nonlinear gravity effects.

Observations may reveal deviations from Kerr black hole metrics.

Potential to detect effects of extra dimensions and massive gravitons.

Abstract

This is a whitepaper submitted to the 2010 Astronomy Decadal Review process, addressing the potential tests of gravity theory that could be made by observations of gravitational waves in the milliHertz frequency band by the proposed ESA-NASA gravitational wave observatory LISA. A key issue is that observations in this band of binary systems consisting of black holes offer very clean tests with high signal-to-noise ratios. Gravitational waves would probe nonlinear gravity and could reveal small corrections, such as extra long-range fields that arise in unified theories, deviations of the metric around massive black holes from the Kerr solution, massive gravitons, chiral effects, and effects of extra dimensions. The availability of strong signals from massive black hole binaries as well as complex signals from extreme mass-ratio binaries is unique to the milliHertz waveband and makes LISA a particularly sensitive probe of the validity of general relativity.