second post-Minkowskian order and behaves as u-2 for large retarded time u. This result
follows from the classical soft graviton theorem at order ω ln ω as a low-frequency expansion
of the gravitational waveform with frequency ω. First, we conjecture the gravitational
waveform from the classical limit of the quantum soft graviton theorem up to sub-subleading
order in a soft expansion, and then we derive it for a classical scattering process without any …