# RIKEN Lunch Seminar

## "Complex saddle points of path integrals"

#### Presented by Semeon Valgushev, BNL

Thursday, May 23, 2019, 12:00 pm — Building 510, Room 2-160

In this talk, we discuss the physical role of complex saddle points of path integrals. In the first case study, we analyze saddle point structure of two-dimensional lattice gauge theory represented as Gross-Witten-Wadia unitary matrix model. We find that non-perturbative physics in the strong coupling phase can be understood in terms of new family of complex saddle points those properties are connected to resurgent structure of the 1/N expansion. In the second case study, we discuss the sign problem in fermionic systems at finite density and the possibility to alleviate it with the help of defomations of integration contour into complex space on the example of two-dimensional Hubbard model.

Hosted by: Yuta Kikuchi

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