First principles electromagnetic responses in medium-mass nuclei: Recent progress from coupled-cluster theory

We review the recent progress made in the computation of electromagnetic response functions in light and medium-mass nuclei using coupled-cluster theory. We show how a many-body formulation of the Lorentz integral transform method allows to calculate the photoabsorption cross sections of ^{16, 22}O and ⁴⁰Ca. Then, we discuss electromagnetic sum rules, with particular emphasis on the electric dipole polarizability, α_D. By including triples corrections in coupled-cluster theory, we revisit ⁴⁸Ca, for which, beside the electric dipole polarizability, we had previously investigated the neutron and proton radii, as well as the size of the neutron-skin thickness (G. Hagen et al. Nat. Phys. 12, 186 (2016)). We show that correlations among these observables still hold, albeit a better agreement with experiment is obtained for α_D and the prediction of a small neutron-skin thickness is further corroborated.