Interaction Expansion of the Partition Function with Action Shifts

In this work, we systematically explore the inclusion of shift terms in the action of Anderson impurity models and their effect on the interaction expansion continuous-time quantum Monte Carlo method. Such terms can either be used absorb the low-order contributions to the series or (approximately) "bosonify" the system.

We explore the behavior of the average sign and the mean expansion order of the series when varying the shift terms for impurity models with general interactions and bath geometries. This is particularly relevant when the impurity model is used as auxilary system of quantum embedding theories such as GW+DMFT or self-energy embedding.