Speaker
Description
The study of Quantum Chromodynamics (QCD) at non-zero baryonic density from first principles is notoriously hard due to the infamous sign problem. One way to potentially by-pass the sign problem is the complex Langevin approach, which is based on a complexification of the underlying field manifold. While this method does not suffer from a sign problem, it is plagued by its own set of shortcomings, which will be the main topic of this talk. In particular, we will discuss the problem that complex Langevin simulations sometimes produce incorrect results despite apparently converging correctly. Using simple toy models, we outline how correct results may be recovered by introducing a so-called kernel into the complex Langevin equations. Moreover, we elaborate on the origin of wrong convergence in the "absence of boundary terms" (which is sometimes viewed as a criterion for correctness) and trace it back to an interplay of different competing so-called integration cycles.
