Use of quantum field theory in cryogenics
Jurij Avsec, Milan Marčič
In engineering practice, processes are of vital importance. Quantum field theory (QFT) was used to calculate thermodynamic properties of state. A mathematical model of a weakly coupled highly degenerate quantum field was developed. The thermodynamic properties of state were calculated for hydrogen and methane with the help of QFT of many particle systems and the finite temperature formalism, and the Feynman – Dyson perturbation theory was used. An expression for the grand potential of normal Maxwell – Boltzmann systems was developed with the help of Green temperature functions and Feynman diagrams.