GWMODELS. Next-generation models of gravitational-wave sources: harnessing the small-mass-ratio limit

We are now six years into the age of gravitational-wave astronomy. When operating, the LIGO-Virgo-KAGRA network of detectors observe roughly one signal every week, each one generated by the dramatic inspiral and merger of two compact objects. For the first time, we are able to observe the two-body problem in its most extreme regime and probe the nature of the strongly gravitating objects -- black holes and neutron stars -- that form these systems. Among other things, this has unveiled a universe teeming with black holes.

But detecting and interpreting gravitational-wave signals requires highly accurate theoretical models. Future (and even current) detectors demand vital improvements to those models, particularly in one important regime: binaries with a large mass disparity, in which one object is tens to millions of times heavier than the other. These systems contain a unique trove of information about the nature of black holes, their history, and the validity of general relativity, but they are currently not well modelled.

My ERC programme will provide the first complete, accurate model of small-mass-ratio binaries, using a perturbative method called self-force theory, in which the ratio of small mass to large mass is treated as a small parameter. This model will go far beyond my recent breakthrough "post-adiabatic" self-force waveforms by accounting for eccentricity, the spin of both bodies, planar precession, orbital resonances, the final merger, and possible environmental effects and deviations from general relativity. By exploiting the unique power of the small-mass-ratio limit, my team will also make new inroads in post-Minkowskian theory and black hole scattering; in tidally deformed bodies and a novel method of accelerating numerical relativity simulations; and in building a universal model of the relativistic two-body problem. This will provide a host of the advances that are critically needed for next-generation gravitational-wave science.