A simple approach towards the sign problem using path optimisation

Understand

We suggest an approach for simulating theories with a sign problem that relies on optimisation of complex integration contours that are not restricted to lie along Lefschetz thimbles.

• To that end we consider the toy model of a one-dimensional Bose gas with chemical potential.
• We identify the main contribution to the sign problem in this case as coming from a nearest neighbour interaction and approximately cancel it by an explicit deformation of the integration contour.
• We extend the obtained expressions to more general ones, depending on a small set of parameters.