Exchange-correlation excitons in plasma media: A Monte Carlo method and the sign problem

To take into account the interference effects of the Coulomb and exchange interactions of electrons, a new representation of the density matrix in terms of the path integral in the canonical ensemble at finite temperatures is developed. The developed representation makes it possible to reduce the effect of the “sign problem” in the simulation of fermionic particle systems by a Monte Carlo method. The results obtained for pair distribution functions in a plasma and a homogeneous electron gas indicate the formation of exchange-correlation excitons. This physical effect has not previously been observed in the simulation of plasma media using a Monte Carlo method.