Regular Article - Theoretical Physics
Nuclear response functions with low-momentum interactions
Physics Department, University of Arizona, 85721, Tucson, AZ, USA
* e-mail: firstname.lastname@example.org
Accepted: 15 March 2019
Published online: 16 May 2019
Linear density response functions for nuclear matter are calculated with separable 1 S 0 and 3 S 1 2-nucleon interactions obtained from experimental phase-shifts by inverse scattering techniques. It has been shown that results of nuclear matter binding energy Brueckner calculations with these potentials agree closely with those using realistic Bonn interactions. It has also been shown that low-momentum versions give binding energies (nearly) independent of momentum cut-offs fm-1. Shown here is that the rank-one version of the separable interaction (for the S-states) yields a near agreement between a second-order and an all-order (Brueckner) binding energy calculation. Second order calculations of response functions are then made with this version using a method that Kwong and Bonitz used for the Coulomb gas. It is based on time-evolving two-time Green’s functions by Kadanoff-Baym (KB) equations. The effect of correlations, going beyond the conventional HF+RPA method, is included by “dressing” the Green’s function propagators with time-dependent complex self-energies in addition to the real HF-field. It would be of interest to see if the calculated response is also, like the binding energy, independent of cut-offs larger than fm-1. That would require using separable potentials of a higher rank, not accommodated by the present computer program. Some results with a 1.5 fm-1 cut-off are however also shown below together with those with a 2.0 fm-1 cut-off. The KB-equations are time-evolved until the nuclear medium is fully correlated. The time-dependent density response to an external perturbation is then registered and Fourier transformed to obtain energy-dependent density response functions. Most previous calculations have been made with in-medium effective (e.g., Gogny or Skyrme) interactions. The medium dependence is in the present calculations contained in the second-order terms.
© Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature, 2019