title: A new geometric invariant on initial data for the Einstein equations.
abstract: For a given asymptotically flat initial data set for Einstein equations a new geometric invariant is constructed. This invariant measures the departure of the data set from the stationary regime; it vanishes if and only if the data are stationary. In vacuum, it can be interpreted as a measure of the total amount of radiation contained in the data.
authors.affiliation: Albert-Einstein-Institut, am Mühlenberg 1, D-14476 Golm, Germany. dain@aei.mpg.de
authors.forename: Sergio
authors.initials: S
authors.lastname: Dain