Method to Obtain Bounds on the Equation of State of Cold Nuclear Matter from Imaginary Chemical Potentials
Phys. Rev. Lett. 136, 181901 – Published 7 May, 2026
DOI: https://doi.org/10.1103/7zxr-j397
Abstract
The sign problem in numerical calculations of the QCD Euclidean space path integral of QCD with a chemical potential vanishes if the chemical potential is imaginary. Moreover, calculations of the partition function with imaginary chemical potentials are equivalent to calculations with Lagrange multipliers enforcing the current density. At zero temperature, Lorentz boosts allow one to deduce properties of systems with both number density and current density from properties of systems with a current density alone; this allows both upper and lower bounds to be determined for the equation of state in the form of energy density as a function of number density.
