Quasilocal energy in modified gravity

Abstract

A new generalization of the Hawking–Hayward quasilocal energy to scalar–tensor gravity is proposed without assuming symmetries, asymptotic flatness, or special spacetime metrics. The procedure followed is simple but powerful and consists of writing the scalar–tensor field equations as effective Einstein equations and then applying the standard definition of quasilocal mass. An alternative procedure using the Einstein frame representation leads to the same result in vacuo.