Factorization of static perturbation theory for weakly coupled systems using imaginary time
Georg Jansen
Phys. Rev. A 113, L030201 (2026) - Published 3 March, 2026
The author show that a reformulation of Rayleigh-Schrödinger perturbation theory in terms of imaginary time-dependent autocorrelation functions allows to write the energy of interaction between weakly coupled quantum systems with the help of integrals containing products of imaginary time cross correlation functions for the individual systems. Thus an alternative to the standard Casimir-Polder expression for the London dispersion energy is obtained.

















