Parametrized path integral formulation for large fermion systems

TL;DR

This paper introduces a parametrized path integral approach to mitigate the fermion sign problem in large fermion systems, enabling accurate energy predictions beyond traditional methods.

Contribution

It develops a new parametrized path integral formulation and explores its validity, providing a practical way to approximate energies in large fermion systems where direct sampling fails.

Findings

Accurate energy predictions for large fermion systems using the new method.

Identification of conditions under which the method is valid.

Discovery of a universal relation for high temperature and strongly interacting particles.

Abstract

The exchange antisymmetry between identical fermions gives rise to the well known fermion sign problem, in the form of large cancellation between positive and negative contribution to the partition function, making any simulation methods which directly sample this partition function exponentially difficult to converge. In this work, we employ path integral molecular dynamics (PIMD) and build upon the recently discovered fictitious particle model to investigate the fermion sign problem further. We consider the validity and invalidity condition for the method of parametrized path integral formulation of the partition function and extrapolation to circumvent the fermion sign problem. For the valid region of our method, our simulation shows that we may give accurate prediction of the energy for large fermion systems, which is much beyond the capability of the direct sampling in the traditional method. In particular, we find and verify a simple universal relation for high temperature noninteracting particles or strongly repulsive interacting particles at low temperatures.