Origin of kinetic-energy discrepancy in liquid 4He PIMC calculations

Ascertain the origin of the approximately 0.1 K systematic difference in the expectation values of the kinetic energy per particle between the present path-integral Monte Carlo calculations using the worm algorithm and previously published results for liquid 4He across the superfluid and normal phases.

Background

The authors report very good agreement with the literature and experiment for potential energies but identify a small, systematic discrepancy (~0.1 K) in kinetic energies relative to prior PIMC studies. They validate their kinetic-energy estimator on ideal-gas tests and note algorithmic differences (ambiguities resolved in the reformulated worm algorithm used here).

Resolving the cause of this kinetic-energy discrepancy is necessary to ensure the reliability and reproducibility of PIMC-based first-principles predictions for liquid helium.