Monte Carlo simulations of the electron short-range quantum ordering in Coulomb systems: Reducing the "fermionic sign problem"

To account for the interference effects of the Coulomb and exchange interactions of electrons a new path integral representation of the density matrix has been developed in the canonical ensemble at finite temperatures. The developed representation allows to reduce the notorious ``fermionic sign problem’’ in the Monte Carlo simulations of fermionic systems. The obtained results for pair distribution functions in plasma and uniform electron gas demonstrate the short-range quantum ordering of electrons associated with exchange excitons in the literature. This fine physical effect was not observed earlier in standard path integral Monte Carlo simulations.