We discuss a new approach to solve the sign problem based on deforming the domain of integration in the path integral into complex space, the stationary phase contours ("thimbles") being only one of them. We will discuss conceptual and algorithmic issues in implementing this set of ideas. As an example we will show results of field theories with a fermionic sign problem and/or real time dynamic ... More

I review the status of the Complex Langevin method, which was invented to make simulations of models with complex action feasible. I discuss the mathematical justification of the procedure, as well as its limitations and open questions. Various pragmatic measures for dealing with the existing problems are described. Finally I report on the progress in the application of the method to QCD, wit ... More