Scattering amplitudes for gravitational wave theory
Four years ago, the LIGO/Virgo observation of a black-hole binary merger
heralded the dawn of gravitational-wave astronomy.  The promise of future
observations calls for an invigorated effort to underpin the theoretical
framework and supply the predictions needed for detecting future signals and
exploiting them for astronomical and astrophysical studies.  Ampl2Einstein
will take ideas and techniques from recent years' dramatic advances in Quantum
Scattering Amplitudes, creating new tools for taking their classical limits
and using it for gravitational physics.  The powerful `square root' relation
between gravity and a generalization of electrodynamics known as Yang--Mills
theory will play a key role in making this route simpler than direct classical
calculation.  We will transfer these ideas to classical General Relativity to
compute new perturbative orders, spin-dependent observables, and the
dependence on the internal structure of merging objects.  We will exploit
symmetries and structure we find in order to extrapolate to even higher orders
in the gravitational theory.  We will make such calculations vastly simpler,
pushing the known frontier much further in perturbation theory and in
complexity of observables.  These advances will give rise to a new generation
of gravitational-wave templates, dramatically extending the observing power of
detectors.  They will allow observers to see weaker signals and will be key to
resolving long-standing puzzles about the internal structure of neutron stars.
We will apply novel technologies developed for scattering amplitudes to
bound-state calculations in both quantum and classical theory.  Our research
will also lead to a deeper understanding of the classical limit of quantum
field theory, relevant to gravitational-wave observations and beyond.  The
transfer of ideas to the new domain of General Relativity will dramatically
enhance our ability to reveal new physics encoded in the subtlest of
gravitational-wave signals.