Comparing gravitational-wave memory waveforms

The nonlinear or Christodoulou memory is a non-oscillatory contribution to the gravitational-wave signal that arises from the gravitational-wave stress energy tensor. Extracting the nonlinear memory from numerical relativity simulations has proven challenging, except via the use of Cauchy Characteristic Extraction (CCE). We perform a comparison study of memory waveform modes computed via two methods: the CCE technique and a semi-analytic approach that uses oscillatory (non-memory) waveform modes as input.