Computational Aspects of Canonical-Ensemble Auxiliary-Field Monte Carlo for the Unitary Fermi Gas

The unitary Fermi gas, defined as a collection of spin-1/2 particles interacting at zero range with infinite scattering length, is of interest to a wide variety of problems in many-body physics. Quantum Monte Carlo (QMC) methods are the only theoretical methods with controllable systematic errors for studying such systems and have been widely applied to predict their properties. Calculations at finite temperature and for fixed particle number are important for studying finite-size systems and for pairing phenomena such as the pseudogap. I will discuss computational aspects of such calculations using auxiliary-field quantum Monte Carlo (AFMC), including the validity of using a spherical cutoff in the single-particle momentum, a strategy previously applied to reduce the dimensions of the matrices involved. Without such a cutoff, finite-temperature calculations are considerably more expensive; I will discuss other strategies that can reduce the computational scaling of finite-temperature AFMC calculations.