title: A radiation scalar for numerical relativity.
abstract: This Letter describes a scalar curvature invariant for general relativity with a certain, distinctive feature. While many such invariants exist, this one vanishes in regions of space-time which can be said unambiguously to contain no gravitational radiation. In more general regions which incontrovertibly support nontrivial radiation fields, it can be used to extract local, coordinate-independent information partially characterizing that radiation. While a clear, physical interpretation is possible only in such radiation zones, a simple algorithm can be given to extend the definition smoothly to generic regions of space-time.
authors.affiliation: Department of Physics, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Beetle
authors.forename: Lior M
authors.initials: LM
authors.lastname: Burko