## The Complex Langevin approach to the Sign Problem of Lattice Field Theory

**Speaker:**Casey E. Berger, University of North Carolina, Chapel Hill

**When:**January 29, 2020 (Wed), 04:15PM to 05:15PM (add to my calendar)

**Location:**PRB 595

*This event is part of the HET Seminar Series. *

Quantum field theories with a complex action appear across energy scales, from condensed matter physics to lattice QCD, and they suffer from a sign problem in stochastic nonperturbative treatments. This means that many systems of great interest – such as polarized or mass-imbalanced fermions and QCD at finite baryon density – are extremely challenging to treat numerically. Another such system is that of bosons at finite angular momentum. Experimentalists have successfully achieved vortex formation in supercooled bosonic atoms and have measured quantities of interest such as the moment of inertia. However, the rotation results in a complex action, making the usual numerical treatments of the theory unusable. The use of the complex (Langevin) stochastic quantization is presented to overcome the sign problem and calculate basic properties of interacting bosons at finite angular momentum.