Advances in coupled-cluster computations of nuclei

Abstract:  In this talk I will report on recent advances in ab-initio coupled-cluster computations of nuclei starting chiral Hamiltonians with two- and three-nucleon forces. Using high precision coupled-cluster methods we addressed the quenching puzzle of [beta]-decays in nuclei. We showed that this quenching can be explained from two-body currents and many-body correlations. In particular, we made predictions for the Gamow-Teller decay of the heavy nucleus 100Sn [1,2], and our result is consistent with the recent high precision measurement at RIKEN [3]. I will also show very recent results for medium-mass nuclei and nuclear matter using optimized chiral interactions with explicit delta degrees of freedom. Binding energies, radii, and saturation properties in nuclear matter are improved compared to existing chiral Hamiltonians. We have also started computations of deformed nuclei using a coupled-cluster approach starting from a deformed Hartree-Fock reference state with promising results for nuclei up to mass A˜50. Last, but not least, I will present a new method that allows for the computation of bulk properties of an atomic nucleus for a million of different model parameters in less than one hour on a standard laptop. The equivalent set of ab-initio coupled-cluster computations would require about 20 years. This speedup enables statistical computing of the chiral nuclear Hamiltonian, and entirely new ways to use experimental data across the nuclear chart to generate new knowledge about the strong nuclear interaction [4]. [1] T. D. Morris, et al, Phys. Rev. Lett. 120, 152503 (2018) [2] P. Gysbers, et al, Nature Physics 15, 428-431 (2019) [3] D. Lubos et al., Phys. Rev. Lett. 122, 222502 (2019) [4] A. Ekström and G. Hagen, Phys. Rev. Lett. 123, 252501 (2019)