# Nuclear Theory/RIKEN Seminar

## "Going with the flow: sign problem, Lefschetz thimbles and beyond"

#### Presented by Gokce Basar, University of Maryland

Friday, April 29, 2016, 2:00 pm — Small Seminar Room, Bldg. 510

Monte Carlo method, a robust way of studying field theories and many body systems, suffers from the sign problem when the action is complex. This includes an important set of problems such as most field theories, including QCD, and strong correlated electronic systems at finite density, as well as computation of real time quantities like transport coefficients. I will show that lifting the path integration to a complex manifold provides a way to ameliorate the sign problem, and introduce a new algorithm for carrying on such a computation. I will give some quantum mechanical examples with severe sign problems, including finite density of fermions and real time observables where Monte Carlo simulations can be profitably performed by this method. Finally I will discuss the 3+1d Bose gas with nonzero chemical potential.

Hosted by: Soeren Schlichting

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