Independent time approximation for dynamically interacting multi-electron systems

摘要

We propose an independent time approximation (ITA), defined by simplifying the chronological operator, namely, T similar or equal to T-unc, where T-unc is the uncorrelated limit of the chronological operator T. The concept of the time correlation is analogous to spatial electron correlation In both cases 'correlation' is the difference between an exact result and an uncorrelated Limit. In the uncorrelated ITA the time correlation operator T-cor = T - T-unc is neglected and causality between electrons is lost. In second-order calculations of a two-electron transition the ITA reduces computer time by over two orders of magnitude. Greater savings are expected when higher orders or more electrons are included. [References: 47]