Bibliography of Literature on GW Ab Initio Calculations which use Imaginary Time

The GW Approximation is an ab initio approach to calculating electronic structure which avoids using the Local Density (LDA) Approximation, the Generalized Gradient (GGA) Approximation, or similar density functionals. It goes beyond the Hartree-Fock approximation by including screening and excited state effects, and shares conceptual similarities with MP2 and RPA calculations. Because GW includes dynamics and time/frequency dependence of the system's screening and excited state behavior, a pivotal issue in any GW calculation is the question of how to numerically represent and manipulate time/frequency dependence. While earlier GW calculations generally used a representation in real time/frequency, many recent calculations have used a representation on the imaginary time axis. Imaginary time is important not only for numerics but also because it can enable additional physics such as systems where self-consistent GW is needed or that are strongly interacting, integration with DMFT, and scaling of GW to very large systems. This current text reviews the research literature on imaginary time GW codes and briefly discusses the possibilities for memory and CPU optimizations.