High-powered gravitational news

Abstract

We describe the computation of the Bondi news for gravitational radiation. We have implemented a computer code for this problem. We discuss the theory behind it as well as the results of validation tests. Our approach uses the compactified null cone formalism, with the computational domain extending to future null infinity and with a world tube as inner boundary. We calculate the appropriate full Einstein equations in computational $e$th form in (a) the interior of the computational domain and (b) on the inner boundary. At future null infinity, we transform the computed data into standard Bondi coordinates and so are able to express the news in terms of its standard ${N}_{+}$ and ${N}_{\ifmmode\times\else\texttimes\fi{}}$ polarization components. The resulting code is stable and second-order convergent. It runs successfully even in the highly nonlinear case, and has been tested with the news as high as 400, which represents a gravitational radiation power of about ${10}^{13}{M}_{\ensuremath{\bigodot}}/\mathrm{sec}.$