Real-time Kadanoff-Baym approach to nuclear response functions

Progress in Non-equilibrium Green's Functions

Köhler, H.S.^1 ; Kwong, N.H.^2

Physics Department, University of Arizona, Tucson

AZ

85721, United States^1

College of Optical Sciences, University of Arizona, Tucson

AZ

85721, United States^2

关键词: Bethe-Salpeter equation;    Correlated electrons;    Density fluctuation;    Density response;    Local potentials;    Momentum-dependent;    Response functions;    Time-dependent potentials;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/696/1/012011/pdf
DOI  :  10.1088/1742-6596/696/1/012011

来源: IOP

【 摘 要 】

Linear density response functions are calculated for symmetric nuclear matter of normal density by time-evolving two-time Green's functions in real time. Of particular interest is the effect of correlations. The system is therefore initially time-evolved with a collision term calculated in a direct Born approximation until fully correlated. An external time-dependent potential is then applied. The ensuing density fluctuations are recorded to calculate the density response. This method was previously used by Kwong and Bonitz for studying plasma oscillations in a correlated electron gas. The energy-weighted sum-rule for the response function is guaranteed by using conserving self-energy insertions as the method then generates the full vertex-functions. These can alternatively be calculated by solving a Bethe -Salpeter equation as done in works by Bozek et al. The (first order) mean field is derived from a momentum-dependent (non-local) interaction while 2ndorder self-energies are calculated using a particle-hole two-body effective (or residual) interaction given by a gaussian local potential. We show results of calculations of the response function S(,q0) for q0= 0.2, 0.4 and 0.8fm-1. Comparison is made with the nucleons being un-correlated i.e. with only the first order mean field included. We discuss the relation of our work with the Landau quasi-particle theory as applied to nuclear systems by Babu and Brown and followers.