SciPost Phys. 6, 040 (2019) Comparing many-body approaches against the helium atom exact solution Jing Li1,2, N. D. Drummond3, Peter Schuck1,4,5 and Valerio Olevano1,2,6? 1 Université Grenoble Alpes, 38000 Grenoble, France 2 CNRS, Institut Néel, 38042 Grenoble, France 3 Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom 4 CNRS, LPMMC, 38042 Grenoble, France 5 CNRS, Institut de Physique Nucléaire, IN2P3, Université Paris-Sud, 91406 Orsay, France 6 European Theoretical Spectroscopy Facility (ETSF) ?
[email protected] Abstract Over time, many different theories and approaches have been developed to tackle the many-body problem in quantum chemistry, condensed-matter physics, and nuclear physics. Here we use the helium atom, a real system rather than a model, and we use the exact solution of its Schrödinger equation as a benchmark for comparison between methods. We present new results beyond the random-phase approximation (RPA) from a renormalized RPA (r-RPA) in the framework of the self-consistent RPA (SCRPA) originally developed in nuclear physics, and compare them with various other approaches like configuration interaction (CI), quantum Monte Carlo (QMC), time-dependent density- functional theory (TDDFT), and the Bethe-Salpeter equation on top of the GW approx- imation. Most of the calculations are consistently done on the same footing, e.g. using the same basis set, in an effort for a most faithful comparison between methods. Copyright J. Li et al. Received 15-01-2019 This work is licensed under the Creative Commons Accepted 21-03-2019 Check for Attribution 4.0 International License.