Lefschetz thimble Monte Carlo for many body theories: application to the repulsive Hubbard model away from half filling

Understand

Recently, a new method, based on stochastic integration on the surfaces of steepest descent of the action, was introduced to tackle the sign problem in quantum field theories.

• We show how this method can be used in many body theories to perform fully non-perturbative calculations of quantum corrections about mean field solutions.
• We discuss an explicit algorithm for implementing our method, and present results for the repulsive Hubbard model away from half-filling at intermediate temperatures.
• Our results are consistent with those from the recent state of the art cluster dynamical mean field theory calculations.