title: Extraction of gravitational waves in numerical relativity.
abstract: A numerical-relativity calculation yields in general a solution of the Einstein equations including also a radiative part, which is in practice computed in a region of finite extent. Since gravitational radiation is properly defined only at null infinity and in an appropriate coordinate system, the accurate estimation of the emitted gravitational waves represents an old and non-trivial problem in numerical relativity. A number of methods have been developed over the years to "extract" the radiative part of the solution from a numerical simulation and these include: quadrupole formulas, gauge-invariant metric perturbations, Weyl scalars, and characteristic extraction. We review and discuss each method, in terms of both its theoretical background as well as its implementation. Finally, we provide a brief comparison of the various methods in terms of their inherent advantages and disadvantages.
authors.affiliation: Department of Mathematics, Rhodes University, Grahamstown, 6140 South Africa.
authors.forename: Nigel T
authors.initials: NT
authors.lastname: Bishop
authors.affiliation: Institute for Theoretical Physics, 60438 Frankfurt am Main, Germany ; Frankfurt Institute for Advanced Studies, 60438 Frankfurt am Main, Germany.
authors.forename: Luciano
authors.initials: L
authors.lastname: Rezzolla
keywords: Binary mergers; Black holes; Gravitational wave extraction; Neutron stars; Numerical relativity