Speaker : C. Galley

Title : Fast and accurate evaluation of black hole Green’s functions using surrogate models

Abstract : Green’s functions in black hole spacetimes are useful for computing many physical quantities for self-force and wave propagation problems. Numerical solutions of Green’s functions in black hole spacetimes successfully and accurately describe the transient features present after quasi-local expansions break down but before calculations of late-time tail effects become accurate. However, the numerical approach faces important challenges because solutions are slow to generate and result in data files that can be too large for practical uses. Reduced-order modeling techniques, which recently have been successfully applied to similiar problems in numerical relativity, are ideally suited to overcome these challenges. I describe how to build a reduced-order model that can be evaluated as a substitute, or surrogate, for solutions of the black hole Green’s function equation. The resulting surrogate accurately represents the Green’s function and can be evaluated much faster than the numerical solutions are produced. I will show how the surrogate is built and discuss potential applications where the surrogate may be useful, which include self-consistent evolutions and waveforms for intermediate/extreme mass ratio binaries as well as higher-order self-force corrections.