Initial correlated states for the Generalized Kadanoff--Baym Ansatz without adiabatic switching-on of interactions in closed systems

TL;DR

This paper introduces a method to define equilibrium correlated states within the GKBA framework for closed systems, eliminating the need for adiabatic switching-on of interactions, demonstrated on a Hubbard-dimer model.

Contribution

It extends the GKBA approximation to self-consistently generate equilibrium correlated states without adiabatic switching, simplifying initial state preparation.

Findings

Successfully applied to a Hubbard-dimer model

Avoids adiabatic switching for initial state preparation

Demonstrates computational efficiency and accuracy

Abstract

We reconsider the Generalized Kadanoff--Baym Ansatz (GKBA) approximation for non-equilibrium Green's functions and extend it to self-consistently define an equilibrium correlated (within GKBA) state in closed systems. The advantage of the proposed prescription is to avoid the preparation of the initial equilibrium correlated state via adiabatic switching-on of the correlations. A simple model system, namely a Hubbard-dimer, is used to illustrate aspects of the computational implementation and performance of the new scheme.