Wave-function-based emulation for nucleon-nucleon scattering in momentum space

Emulators for low-energy nuclear physics can provide fast & accurate predictions of bound-state and scattering observables applications that require repeated calculations with different parameters, such as Bayesian uncertainty quantification. In this paper, we extend a emulator based on the Kohn variational principle (KVP) to momentum space (including coupled channels) arbitrary boundary conditions, which enable mitigation spurious singularities known anomalies. We test it modern chiral nucleon-nucleon (NN) interaction, including emulation channels. comparisons between Lippmann-Schwinger equation our KVP momentum-space representative set neutron-proton (np) observables, also introduce quasi-spline-based approach KVP-based emulator. Our findings show while there are some trade-offs accuracy speed, all three emulators perform well. Self-contained Jupyter notebooks generate results figures in paper publicly available.