Characteristic extraction in numerical relativity: binary black hole merger waveforms at null infinity - General Relativity and Quantum CosmologyReport as inadecuate




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Abstract: The accurate modeling of gravitational radiation is a key issue forgravitational wave astronomy. As simulation codes reach higher accuracy,systematic errors inherent in current numerical relativity wave-extractionmethods become evident, and may lead to a wrong astrophysical interpretation ofthe data. In this paper, we give a detailed description of theCauchy-characteristic extraction technique applied to binary black holeinspiral and merger evolutions to obtain gravitational waveforms that aredefined unambiguously, that is, at future null infinity. By this method weremove finite-radius approximations and the need to extrapolate data from thenear zone. Further, we demonstrate that the method is free of gauge effects andthus is affected only by numerical error. Various consistency checks revealthat energy and angular momentum are conserved to high precision and agree verywell with extrapolated data. In addition, we revisit the computation of thegravitational recoil and find that finite radius extrapolation very wellapproximates the result at $\scri$. However, the non-convergent systematicdifferences to extrapolated data are of the same order of magnitude as theconvergent discretisation error of the Cauchy evolution hence highlightingthe need for correct wave-extraction.



Author: C. Reisswig, N. T. Bishop, D. Pollney, B. Szilagyi

Source: https://arxiv.org/







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